Lucky you,
I've been searching for one similar to that for a long time. When I was an apprentice we were only allowed to use a dial indicator on bright or machined stock. For black bar we used a similar idea to the Koch. it had a ball end which rested on the work and formed the horizontal part of a bell crank. The vertical part of the bell crank formed a point against a scale on the body and worked against a spring. The working range was about 0.050"
Best Regards
Bob