How this cross reference works

Format

0         1         2         3         4         5         6         7
0123456789012345678901234567890123456789012345678901234567890123456789012345

    ISCR#         USA      Germany   France      GB      Swiss    reserved
============================================================================
YYYYMMDD.##A   |         |         |         |         |         |         |
============================================================================


Columns 0..14 contain the Internet Stamp Cross Reference (ISCR) Number, 
broken down as follows:

    YYYY  = nominal year of issue in the common era. (see note 3)
    MM    = nominal month of issue. If not known use 00
    DD    = nominal day of issue. If not known use 00
    .     = decimal point or period (ASCII 46).
    ##.## = denomination
    A     = varieties, e.g. 'A', 'B', etc.
 
Columns 15, 25, 35, 45, 55, 65, and 75:

   |     = vertical bar (ASCII 124)

Columns 16..24: USA Catalog #

Columns 26..34: Germany Catalog #

Columns 36..44: France Catalog #

Columns 46..54: GB Catalog #

Columns 56..64: Swiss Catalog #

Columns 66..74: Reserved (see note 2).

Columns 76..120: Description. This is nominally ISO Latin-1 (or ASCII).
        ISO Latin-15 may also be used. If you don't know what ISO Latin-1,
        ISO Latin-15, or ASCII are, that's okay, don't worry about it;
        just send what you've got and I'll figure it out.

Note 1: Taking suggestions for a widely used catalog.

Note 2: Reserved for country specific catalog, e.g. South African Colour
        Catalogue.

Note 3: In the event that varieties are discovered after the issue date
        the nominal issue date applies to all varieties, which receive
        A, B, C, etc., designation.  Reprints and reissues receive their 
        own ISCR# reflecting the reprint/reissue date.

        When the official issue date is not known, as is the case with
        many early issues, use Earliest Known Usage (EKU). If that's
        not known use 00 for the issue day. If the month is also not 
        known use 00 for the issue month.

        All dates are Common Era (C.E.), more commonly known in the "west"
        as Anno Domini (A.D.)

Example

US
                   USA     Germany   France      GB
============================================================================
...
19431123.00    | C3      |         |         |         |         |         | Jenny Airmail
19431123.00A   | C3a     |         |         |         |         |         | Invert Jenny
...
============================================================================