About the 1A file & the 1B file

1A and 1B are two totally different lists:
1A is based on matrix numbers and is as complete as possible.
1B is based on catalogue numbers (side numbers, face numbers) and refers the user back to the 1A file.

Both the 1A file and its parallel 1B version contain:
(1) material recorded by The Gramophone Company for its Gramophone and/or Zonophone labels. Zonophone was a cheap sub-label sometimes used instead of the GramCo label.

(2) Victor : material legitimately leased from The Gramophone Company by Victor, its sister company.

(3) Polyphon (inside Germany) and Opera Disc (USA) : post take-over (semi- legitimate).

(4) Several bootleg (pirate) labels use GramCo material illegitimately.

MATRIX NUMBERS
A matrix number is a unique number, linked to a certain recording. Normally it forms part of a chronological sequence of recordings made during a certain recording session or belongs to a subsequent different recording session.

A matrix number nearly always consists of a numerical part (one or more digits) preceded or followed by a letter or a letter combination. While the numerical part of the matrix number indicates the chronological order, the letter or letter combination contains extra information: it not only gives us a clue about the size of the recording (7”, 10” or 12”), but at the same time it tells us which recording engineer made the recording.

Normally the matrix number can be found stamped into the empty/dead wax between label and end of groove. Embossed. It can often be found in handwritten form under the paper label.
As a rule it is never printed on the paper label. The 1900 recordings, which have no paper label, have the matrix number scratched into the label area.