Starting with the C-model, serial numbers were engraved next to the 1-key of the leftmost column of keys, a practice that was to continue thru the J-models.
To the best of my knowledge, all Compts also had a matching number stamped into the left side frame of the mechanism.
Clearly, if a model started with a mod-5000 number, its safe to assume that the first machine of that model carried that number. What can not be assumed is what number was on the very last machine of that model!
Note that it cannot be assumed that a new model would carry the next logical "mod" number since, it appears, there was something of a "numbering war" taking place with competitors; sort of a "King of the Hill" mentality. That this occurred with the wooden-cased models is evident since the last known such machine is under 7000 and the next (A) model started with 15,000, skipping the obvious 10,000 choice.
The serial ranges shown on The Models page and elsewhere indicate the starting mod number and sometimes the earliest and/or highest discovered numbers.
Following is a list of all shoebox models and their known serial number ranges together with a "best estimate" of the number produced...
Model Start# First# Last# Max# Comments ------ ------- ------ ------ ------ ------------------------------ Wooden 10? 61 6244 6244 earliest 8 machines unserialized A 15000 15242 20603 5604* B 25000 25517 33461 8462* Last# is a Sterling model (£s.d.) C- 35000 35606 38602 3603 C+ 40000 40137 48648 8649 D 49001 49000 49154 154 Src: Amer Digest E 54000 55376 61612 7613* most converted or destroyed F 100000 100249 142337 42338 H 200000 200109 248508** 48509 Last# is a British Greenee (£s.d.) J*** 245489** 245489 346384 95385 only 7 known below #250,000 Maximum production count: 224410 (shoebox models only) (over 80% of all shoebox models made were Fs, Hs and Js) notes: *total questionable (few actually found, annomolies in sequence, etc) **last Hs and first Js mixed within the 247,000 range ***includes Supertotalizer