More Flea market finds

[chucketn]

Had a good day at the local flea market. Picked up an old JTSlocomb 2-3” outside micrometer. Cananyone provide model # or any other info?
Pics here: JTSlocomb mics
The one I have looks like the one in the middle.
I did find a scan of some other Slocomb mikes but not thisone. Does anyone have the original usersmanual for this style? What is the knurled knob on the end of the barrel for?
Anyone have the spanner for adjustment that could give methe dimensions? Are these spanners available or can I make one?
Chuck

 

[Till]

What is the knurled knob on the end of the barrel for?

It's a small ratchet that allows you to apply the same amount of pressure on the workpiece every time.