There were four different sizes of American style (Waltham) lathes and collets used in the American Watch Co. They were the Nashua #1 (4.5 mm), Nashua #2 (8.25 mm), Nashua #3 (11.25 mm) and Nashua #4 (20.03 mm).
The four sizes of Waltham factory lathe collets are pictured with their Master gauges to check: angle, body diameter, thread diameter, and thread fit.
The second set of gauges are used to check the angle in the lathe spindle for Nashua #1, #2 and #3 collets.
Standard gauge Church machine chuck.<<more text>>.
This gauge is used to check the metric threads of screws used on the watchmaking machinery.
These brass gauges are samples to show the 7 different sizes of number and letter stamps used in the factory. These comparisons were done by eye since the exact shapes were not critical.