This is a “Dial Test Indicator Back Plunger Set”. A friend gave it to me for minor services rendered.

It appears to be complete, as all the recesses are occupied.

The indicator has a plunger rod sticking out the back, with a travel range of 0.200. It is threaded 5-44 UNF, and there are 3 buttons to fit.

One of the two rods is threaded 1/4-28 and fits the C-clamp device. The other is threaded 10-32 and fits the bar for the tool post of any lathe larger than my Sherline. However, 10-32 is the standard tooling thread for Sherline, so I can mount assemblies to the lathe or mill slides with just a simple spacer and a T-nut.

Many set-ups are of course possible. Here is one to check the tangent of the headstock angle, before making a taper cut.

And here is a set-up to check the interior profile of a small bore, using the rocker gizmo.