+1 on what Mike said...
I decided I needed a .0001 indicator, ordered up a Bestest 7023-3 from MSC on a %off sale a few months ago, thought I got a pretty good price (lowest I could find anywhere). Unpacked it the second it arrived...the label on the plastic case did not say "SWISS MADE"...uhoh methinks something is awry here. Sure enough the face of the indicator does not say swiss made either. Buyer beware indeed, I have no idea where it was assmbled/made. Having said that, it appears identical in terms of materials and workmanship, including the plastic case, as my genuine swiss made Bestest. Disappointing though to pay swiss made pricing and have it made somewhere else.
That Compac Mike linked appears to be a steal at that price, and is a sweet indicator. I'm not sure that is corrosion on the screw face...lordy am I tempted on that one regardless, but I already have 2 half-thou indicators and the finance department would blow a fuse...still tempted though. I seem to have developed a fetish for swiss indicators thanks to the helpful folks on this forum.
My first indicator when i was starting out and didn't know any better was this one
https://www.ebay.com/itm/030-Dial-T...520798?hash=item19fbf8109e:g:uogAAOSwv~1aTWD3. Have to say it has worked just fine and still does, despite taking some unintentional abuse. If I were on a tight budget it would, and did, get me started.
Agree buying used can be a crapshoot. I haven't been burned yet but then I've only bought 2 used. One is a Compac 225GA vertical off ebay in wonderful condition, extremely happy with it. The other was one I couldn't resist, an Alina 41-628, another vertical style, although with small face but it's just so darn cute (yup my name is Kurt and I have an indicator problem), that I bought from Ideal Precision out of their used/reconditioned section, even came in the original wood case.
I have 2 Noga bases, the small and medium with fine adjust on the base...love them.
With gun barrels you are using the indicator as a comparator, taking readings off the lands or grooves not both, whichever suits your fancy; this is how barrels are indicated. As such switching out stems is not an issue since you are only comparing position and not concerned with absolute dimension. However I do have an Interapid 312B-15 long arm for such work (did I mention I have an indicator problem).