Gruen movement caliber numbering

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Gruen movement caliber numbering

#1 Post by MikeTheWatchGuy » Sun Feb 05, 2017 12:54 pm

I posted some time ago about the Gruen movement caliber numbering scheme... and my inability to describe how it works... with a desire to figure it out. It's no news that I'm poking at serial numbers, timelines, dating charts, etc. In the back of my head, and scattered across web pages and spreadsheets I've tried to list some of the descriptors that could go into the numbering scheme.

Here is a table similar to the one in the Gruen Movement Catalog
SNAG-0305.jpg (41.38 KiB) Viewed 588 times

Can you list a few variables or "features" that may be part of what goes into creating a movement caliber??

A few of the features / naming conventions we know include
21 jewel varieties add a "1" to the end of the number. 335 -> 3351, 325 -> 3251
Some 17 jewel versions added a "7" to the end. 106 15j, 1067 17j
7 and 15 jewel movements change the last digit 500 17 jewels, 501 15j, 502 7j

Are there naming conventions from other brands available that could give us a hint for how Gruen may have named them?

I'm convinced that there was a naming convention that was used. Maybe it's already clear to other people, but I sure don't understand it fully.

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