Isabelle Release Address Identifier

The Isabelle Release Address Identifier (IRAI) is a new identifier for dream towns created in ACNL (Animal Crossing: New Leaf). Isabelle, a dog from ACNL, runs this system. It consists of 4 elements: a prefix element, an issuer element, a work number element and a check character element.

The system was rolled out on 31 October 2015 (2 years, 4 months, 3 weeks and 1 day after ACNL was released in the west) to track the dream towns and prevent malicious attacks.

The IRAI can be only issued to a dream town only if a user submits the dream town in the Isabelle's official website (https://www.isabelle-the-dog.net/).

IRAI structure plans
The IRAI was supposed to have 11 digits (alphanumeric) without a check digit but this plan never came into fruitition. In 2013, the system was expanded to include the prefix 1B and the alphanumeric checksum. By 2014, it was revised with the prefix 1B, 19 digits (alphanumeric) and the alphanumeric checksum which the IRAI uses this structure today.

A smaller version of IRAI (called IRAI-S) does not use a check digit and the prefix '1B', instead has only 19 digits followed by a two-digit random number between 00 and 99. This version is uncommon (only less than 1000 dream towns use this). For example, HA710085P47L0M2A13688 may correspond to 1BHA710085P47L0M2A1361 in the normal version.

Structure
The Isabelle Release Address Identifier contains 4 elements:

Prefix element (2 characters)
 * '1B' denotes an IRAI.

Issuer element (4 characters)
 * A unique 4-character code of the character responsible for allocating the IRAI, issued by Isabelle. There are over 460 issuers. The first character of the issuer element is taken from the issuer name's first letter. Harry Potter's issuer code, for example, is HA71. Isabelle is I207. You can apply for an issuer code at https://www.isabelle-the-dog.net/irai/apply-an-issuer-code.

Work number element (15 characters)
 * Uniquely identfies a user-submitted dream town assigned to Isabelle's official website. The work number element is a random alphanumeric string.

Check character element (1 character)
 * The check character is calculated from the prefix, issuer and the work elements according to ISO 7064 MOD 37, 36.

Writing Down Isabelle Release Address Identifier
When the IRAI is written, printed or visually presented online, four elements must be separated by a colon. For clarity, it can be also be prefixed by 'IRAI:'. When an IRAI is presented, the font used should distinguish between the digits 1 and 0 and letters I and O. A recommended font to be used is Consolas; but Inconsolata and other fonts are also available.

For example, all strings denote the same IRAI:
 * 1BI207ABCDEF12345678GG
 * 1B:I207:ABCDEF12345678G:G
 * IRAI:1B:I207:ABCDEF12345678G:G

Where:
 * 1B - the prefix element
 * I207 - the issuer element
 * ABCDEF12345678G</tt> - the work number element
 * G</tt> - the check character element