Waltham serial numbers are available from 3 major sources besides the observations of actual watches. Around 1900 the company had ledger books prepared from what appears to be inventory cards. The whereabouts of the original cards is not known. The ledger books were handwritten in multiple copies by a Boston Transcription Firm. At the time they were made, additional copies could be ordered by number.
One of the surviving sets of numbers from 1,001 to 1,500,000 was reproduced by Heart of American Press and is available from them at www.hoapress.com. The second set of numbers from 1,500,001 to 7,555,000 was copied from a book at the Charles River Museum by Joe Brown and 10 additional copies were made by him. My copy of Joe Brown's copying effort was in turn copied and distributed to volunteers for transcription. The numbers from 1,001 to 1,500,000 have been scanned and are available at the link on this page.
The numbers higher than 7,555,000 are available (along with the earlier numbers) in the printed list last distributed by Waltham in 1954 for use by repairmen in ordering parts. This list combines material from the earlier sources where the compilers felt the differences were not significant and it omits the dates found in the other works. It does include the model designations that are missing from the handwritten records. This book is commonly known as "The Gray Book" because of the color of its cover. Information from this source is marked in gray in many of the report displays.
The transcribed serial numbers now exist in a database on this site. The database is still under development, but the team felt it would be a good idea to get input from more people on possible errors and omissions as well as desired features of the query screens.
Jim Schneider transcribed the Waltham printed list and contributed it to the database project. Jim has a special interest in the 1892 model Walthams and has a web site devoted to them.
Roy Ehrhardt's collection of pictures and line drawings of various watch movements can be viewed on the Chapter 174 web site at Waltham EA Diagrams. If you are trying to identify a private label watch, the drawings can be very helpful.