Help With Surface Gage Scriber

I got a vintage Starrett 257A surface gage from a friend for free. It was rusty, but has beautiful color case hardening. The pic above shows their current version, which is dumbed down in every way. No color case, plain black finish. No ball on the end of the mast. No square scriber on the other end of the mast. At the current price of more than $200 they should be gold plated.

But I digress. Mine is all cleaned up,...

Help With Surface Gage Scriber