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Straus Reference



The Straus Reference was developed by Stane Štraus in the year 2000. The reference's purpose is to systematically categorize polymer (and hybrid) bank notes of the world in a clear, simple, and logical manner. Every bank note issue, variety, and sub-variety is assigned a unique reference number, respectively for each country. This web site and the printed catalog Polymer Bank Notes of the World both use the Straus Reference.

General Rules

The general rules explain the rationale behind the Straus Reference system and the criteria for determining bank note issues, types, varieties, and sub-varieties. The following levels of identification are used:

Country Level

This level identifies a country, from which a particular bank note comes from. Short country names in English are used. These country names can be abbreviated to a three-letter code (according to the ISO 3166 Alpha-3 standard) for special uses (e. g., for an inventory list). The exceptions to the ISO standard are: Central African States (CAS), the European Union (EUR), the Isle of Man (IOM), Northern Ireland (UK)—Northern Bank (NIN), Scotland (UK)—Bank of Scotland (SCB), Scotland (UK)—Clydesdale Bank (SCC), and Scotland (UK)—The Royal Bank of Scotland (SCR). Promotional & test notes use discretionary names and discretionary codes beginning with an X.

Reference Designation

The letter S designates the Straus reference. Hybrid bank notes use the additional letter H after the letter S.

Issue Level

This level identifies specific bank note issues. A bank note issue is considered a separate issue if it significantly differs from other issues and if the issuing authority considers it a separate issue. Significant differences include: (i) country title (such as Commonwealth of Australia vs Australia); (ii) issuing authority title (such as Banque Nationale de la République d'Haïti vs Banque de la République d'Haïti); (iii) denomination (such as 10 vs 50); (iv) substantial design characteristics (substantial differences in bank note design, color, or size). Related issues (i.e., issues that belong to a specific time period and are of uniform design) are grouped together in the order of denomination. This means that within a series of related issues, the 20 denomination will always precede the 100 denomination, even if the 100 denomination was issued before the 20 denomination. Issue numbers are assigned respectively for each country. Bank note issues are denoted by numbers 1, 2, 3, etc. and always preceded by the reference designation (S or SH). The word family denotes several bank note issues that for some reason fit together (usually a set of notes of all denominations with a common design theme).

Type Level

This level identifies specific bank note types. The following types are used:

P (proof bank notes)

A proof note is printed with the purpose of establishing the quality, design and other properties of the printing. Proof notes may be unfinished in design and may be missing certain characteristics (serial number, color, printing phase) that one would see on a finished note. Proof notes are usually made to help the printer and the issuing authority select the design, color, etc. A proof note can sometimes bear a 'specimen' overprint. Cancellation holes may be present. Proof notes are usually scarce and unavailable to the public. Note that fully finished notes with zero serial numbers, which are sometimes referred to as 'presentation specimens,' are included in this category. This category also covers what are sometimes called trial or essay notes. Proof notes are usually not legal tender. Several proof notes are always made for every bank note issue and most of these proof notes are never known to the public. The listing of proof notes is therefore always incomplete. Consequently, only those proof notes that are known to exist is collectors’ hands will be assigned a reference number.

S (specimen bank notes)

A specimen note is printed to familiarize various parties (foreign central banks, commercial banks, law enforcement agencies) with the newly issued currency. Some countries also make them available to the public. A specimen note is a fully finished note, with all the characteristics of a regular circulating note and it always bears a "specimen" overprint (in English and/or in the local language). It usually comes with zero serial numbers and a consecutive specimen number. Cancellation holes may be present. Specimen notes are not legal tender.

R (regular bank notes)

This type comprises all regular, legal tender issues (with the exception of replacement bank notes), including collectors' (commemorative) issues. The same designation (R) is used for regular issues and for collectors' issues as it is sometimes difficult to determine whether a note is a collectors' issue or a regular issue. Since there are no recognized criteria to differentiate between these two types of issues (i.e., there are many 'gray' issues), common designation 'regular issues' is used.

Z (replacement bank notes)

Replacement bank notes are sometimes created by the printer to replace damaged or error notes. Such replacement notes bear a special serial number prefix or a special symbol as a part of the serial number to distinguish them from regular notes and to maintain the consecutive serial numbering sequence. Most frequently, however, replacement notes are indistinguishable from regular notes and they bear no special prefix or symbol. Often they are not required at all, as serial numbering is not consecutive and the numbering skips the damaged notes with no replacement.

X (promotional & test notes)

Promotional & test notes are produced by security printers for a variety of reason, including for in-house testing and development of security features, substrates, inks, machinery, etc., and for displaying their technical capabilities and expertise to central banks and other currency professionals. Promotional & test notes generally—but not always—follow the rules regarding the designation of issue, variety and sub-variety levels. Assignation of issues, varieties and sub-varieties can be discretionary for certain promotional & test notes.

Variety Level

The following characteristics identify specific bank note varieties: (i) minor design characteristics (minor design changes, such as minor and local color changes, changes in signatory titles, etc.); (ii) security features, which are often changed, added, and upgraded; (iii) date (different dates of issue, either as an imprint or as part of a serial number, e.g., AA 96 vs AA 97); (iv) printer (notes printed by different printers are assigned a unique variety-level designation only when there are obvious modifications to the bank note; if there are no obvious modifications, a change of printer is classified on a sub-variety level; (v) printing process (such as offset vs intaglio); (vi) signature; (vii) serial number size, font, format (such as 2-letter vs 3-letter prefix), or color (such as red vs black color), all referring to intended serial number color variations (unintended variations are classified as error notes); (viii) overprint (e.g., a note with a black overprint or with a red overprint). Bank note varieties are denoted by numbers 1, 2, 3, etc. The word series is used to distinguish between different varieties of bank notes (single varieties or multiple varieties) that are significant (for one reason or another), according to the prevalent opinion of the numismatic community. For example, we assign separate varieties for all minor design changes (such as an overprint or local color changes). These minor design changes are considered more or less important (or worthy of being collected) by the numismatic community. When the numismatic community views a certain bank note variety as significant (and thus significantly different from other bank note varieties), we might call this variety (or a group of bank note varieties) a series. Grouping different bank note varieties into a series or calling a certain bank note variety a series in its own right is subjective. The word series here is not to be confused with series letters that appear on certain bank notes (such as those of Mexico).

Sub-Variety Level

The following characteristics identify specific bank note sub-varieties: (i) packaging (such as a cardboard or leather folder, a folder with a single note, or a folder with two notes); (ii) issued form (such as a sheet of 24 notes or a single issued note); (iii) special serial numbers (sometimes special serial number prefixes (such as AA 97 or HK 97) are used to commemorate special occasions or low serial numbers (such as AA 000012) are sold by the issuing authority at a premium); (iv) change of printer, where no obvious modifications to the bank note have been made; (v) series designation (certain countries (such as Mexico) use a special series letter, which is imprinted on the note, usually by lithographic (and not letterpress) process—the word series here is not to be confused with the word series as a specific term on the variety level); (vi) country designation (sometimes a serial number prefix denotes a particular country (such as with the Euro notes); (vii) numbering system (sometimes consecutive numbering is used for certain (usually very low) serial numbering ranges and non-consecutive numbering is used for the remaining serial numbering ranges—additionally, certain special print runs (such as uncut sheets) might use a special serial numbering system). The characteristics above define sub-varieties. They do not determine distinct varieties. Simply placing a bank note in a different folder does not do anything for the note itself—it is still the same note. For the same reason, it is not decisive whether the note is issued as a single note or in an uncut sheet of multiple notes. Furthermore, many bank notes are issued on different occasions with different prefixes and serial number ranges—if we consider a certain prefix or serial number range as being different from another prefix or serial number range, we might as well consider each bank note as being its own unique variety. We do recognize that certain scarcer prefixes or certain low-numbered bank notes rightfully command a premium over what would be a market price for a common note, however, this still does not make them a distinct variety. Lastly, a change of printer results in a distinct variety only when there are obvious modifications to the bank note. Obvious modifications are those recognizable under basic or qualified examination and exclude forensic examination of high-level, covert security features. Different serial numbers (such as AA 111111 or CD 222222) are not viewed as an obvious modification. If there are no obvious modifications, a change of printer is classified on a sub-variety level. Bank note sub-varieties are denoted by small letters a, b, c, etc.

Specific Cases

Apart from the General rules above, there is a gray area of borderline examples, where assigning reference numbers is not straightforward and it sometimes requires a discretionary decision. The text below presents several such specific cases. It aims to explain and rationalize past decisions regarding specific cases and it aims to establish guidelines and precedents for assigning reference numbers in difficult and borderline cases for the future.

Design Changes

Changes in substantial design characteristics define issues; changes in minor design characteristics define varieties. The difference between a substantial design characteristic and a minor one is discretionary. This section attempts to establish some guidelines and precedents for making such discretionary decisions. For changes in substantial design characteristics, refer to General rules / Issue level. For changes in minor design characteristics, refer to General rules / Variety level. For specific examples, see below:

Specific examples of changes in substantial design characteristics (a new bank note issue designation has been assigned):

i. Design change. Example I: Australia S2 redesigned to S3 (orientation bands added in eight places; the issuing authority considered this a new bank note issue). Example II: Romania S6 redesigned to S11 (the clear window was reshaped and redesigned, obverse design was modified; the issuing authority considered this a new bank note issue).

ii. Color change. Example: Australia S2 recolored to S3 (the dominant color changed from gray to violet; the issuing authority considered this a new bank note issue).

iii. Resizing. Example: Romania S6 resized to S11 (the note was resized from 168 x 78 to 147 x 82 mm; the issuing authority considered this a new bank note issue).

Specific examples of changes in minor design characteristics (a new bank note variety designation has been assigned):

iv. Design change. Example I: Brazil S1R1 changed to S1R2 (name "Pedro A. Cabral" changed to "Pedro Álvares Cabral"). Example II: Australian issues of 1992-1999 redesigned in 2002 (additions of names of the persons depicted on the notes; the two signatories changed positions).

v. Local color change. Example I: Australia S4 recolored in 1994 (the portrait on reverse changed from blue to gray). Example II: Samoa S1 received several minor color changes (producing four distinct varieties).

Error Bank Notes

Sometimes, the serial numbering ink is chemically unstable, which can cause slight changes in serial number color. Such unintended and erroneous instances do not warrant a separate variety designation; such notes are deemed to be error notes.Specific examples include: Australia S2 (black/green serial numbers), Papua New Guinea S1 (black/green serial numbers) and Sri Lanka S1 (red/orange serial numbers).

Bank notes such as Australia S1R1 warrant a separate variety listing. The S1R1 note showed technical flaws, which were corrected by using improved technology and an improved production process (resulting in the S1R2 note variety). In comparison, the Zambia S1R1 and S2R1 notes exhibited technical flaws (fading serial numbering ink), which were corrected by using the correct application of the same technology and of the same production process. No separate variety listing is therefore needed and the flawed note is deemed to be an error note.

Non-Legal Tender bank Notes

Kuwait S1 and Kuwait S2 are examples of bank notes that are not legal tender. Nevertheless, they were printed by a security printer (NPA), they are using high-level bank note security, and they were issued/sold by an issuing authority (the Central Bank of Kuwait). We have, therefore, included them in our listing.

How to Use The Straus Reference

When the Straus reference system is used to categorize a specific bank note, the reference should be cited in a certain way. This advances the universal recognition and acceptance of the reference system. Examples of proper, conditional, and improper use are shown in the table below.

Proper Use


i. Vietnam S5 or Fiji SH1

This reference is properly cited at the issue level; the letter H denotes a hybrid bank note.

ii. Australia S1R1 or Fiji SH1R1

This reference is properly cited at the variety level; the letter H denotes a hybrid bank note.

iii. Brunei S3R3a

This reference is properly cited at the sub-variety level.

Conditional Use


i. S7 or S2P2 or S4R1a or SH1

Allowed if the country name is mentioned beforehand.

ii. 8 or 3R1 or 4R1a

Allowed if the country name is mentioned beforehand and if the letter S (denoting the Straus reference system) is directly and clearly linked to the citation (for example, as a heading in the table, where the truncated reference appears).

Improper Use

i. China S1Z or S2R

The type level is present, but the variety level is missing. Not allowed.

ii. Samoa 1 or Brazil 1R1 or New Zealand 5R1c

The letter S is missing. Not allowed.

iii. S2R2A or Singapore S4R1B

The sub-variety designation should not be a capital letter. Not allowed.