Starrett Last Word Dial Indicator

Started going through one of my old tool boxes from my working days (forced retirement at age 42 ;{ ) and ran across this...
and it's NOT A PINBACK BUTTON... WHAT!!!
Not sure of the age on this Starrett Last Word dial Indicator No. 711F
I used this for near 30 years when I was a Mold Maker for the plastic injection mold trade in Detroit suburbs it was given to me by an old timer in the early 70s when I first started building molds after being a bench hand /mold polisher for 2 to 3 years and planned on giving it to some young person starting out but by then everyone wanted the new Interapid Indicator. They still sell what looks like the same Last Word it just has a new model No. (711FSZ) for $160 to $280 depending on attachments.
The small bottle contains a variety of interchangeable Contact Points.
It still works fine with each mark on the dial reading 0.001 of a inch (last time I measured a hair it was 0.002)