Below is a micrometer caliper. In particular, this is a one inch outside micrometer caliper. It measures outside dimensions from zero to one inch by thousandths of an inch. A two inch outside micrometer would measure from one to two inches, and a three inch from two to three inches, etc. This particular “mic” was made by the J.T. Slocomb Company, of Providence, Rhode Island, probably sometime in the 1940’s.
J.T. Slocomb calipers were well-regarded by machinists. They were noted for their robustness and unique means for wear adjustment, which made the calipers last longer (the opposite of the way things are made nowadays). Page 89 of the 1920 catalog is a cutaway view of a model 25 micrometer (below).
Here’s a model 35 and its page in the catalog.
Like most tool companies of the time, the inside of their catalog had a picture of the factory. Not the most impressive building then or now, (see image below) but their product line was only micrometer calipers and countersink drill bits, so a gigantic complex wasn’t necessary. Sometime in the 1950’s, they moved from Providence, Rhode Island to Glastonbury, Connecticut. The old factory (actually their second one in Providence) has been converted to commercial storage.
Below is a scan of the instruction sheet that came with Slocomb micrometers.