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I noticed that there is circular mark in the left hand corner of the motor board trim on our C-19. I assume it needs one of those Official Lab Model medallions. Am I correct? I think there are some different styles and I wonder which one is correct. This is in our local museum and I want to get it right!
Thanks!
Dave D

Francis W. Pratt authored an excellent series on the Diamond Disc for the Antique Phonograph Society.

You can log-in to your APS account, navigate to Articles / Advanced

and in the Search field simply enter Pratt

Several documents will be referenced in the query-result list, but the ones of interest to you will be:

TAP-2015-12
TAP-2016-03
TAP-2016-06_redacted
TAP-2016-09-redacted

I'm sure you will find an authoritative answer there.

If I recall, it had something to do with the number of springs in the motor.

Rod's right - any Edison Disc Phonograph with double mainsprings PLUS the 250-size horn (there were three sizes) was considered an "Official Laboratory Model." The designation didn't appear until late 1915, though, so machines manufactured prior to that time such as the A-250 will not have an "Official Laboratory Model" medallion. (This is also a good reason NOT to refer to the Chippendale as a "Lab Model" since there were others such as the William and Mary.)

There were four different medallions, whose design evolved as more machine models were added to the "Official Laboratory Model" lineup. Checking Fran Pratt's articles will show you these styles and tell you which one is appropriate for the C-19 in question. Actually, you can check this under the "Introductory" articles which are available to the public. Fran's C-250/C-19 Database is there, and there are two documents there which will help you. All you need is the machine's serial number.

https://www.antiquephono.org/edison-c-2 ... -1925-pdf/

Thank you Fran and APS!

George P.

Thank you Rod and George, for the accolades!

Dave, all Edison Chippendales were produced and marketed as "Official Laboratory Model" machines, there were 4 different medallion iterations, dependant on the production period, and as George pointed out the data I shared on the APS website illustrates which medallion would be appropriate for each production time period. Other models were also consider an OLM, as noted by George.

Best,
Fran

Thanks everyone. I now know what is missing and will keep an eye out for it at Union. Of the four medallions illustrated, only once does not mention the model C-250. Since this is a C-19, it makes it easy to know which one to look for.
Dave D