trimos digital height gage

I picked up a non working gage (tvn) probably 30 years old. No touch probe, so it is really an indicator holder.
Found one of the battery terminals had corroded off. Spent an afternoon making a tiny brass tab and soldering it on. Dropped and lost several pieces, oops.

My question is about the hand wheel assembly. There is a lever that engages the fine adjust knob. When I move it the whole assembly moves. It seems to be only a friction fit in the bore, so it takes two hands to engage it. There is a groove on the shaft. Is this supposed to have a wavy washer to retain it? there is also a nylon button in the base under the knob assembly, maybe something missing here?

Any one have a manual that shows this assembly.

Dave

the model is actually tvm300.
Got some new batteries today and was checking the accuracy.
I have a cheap set of gage blocks and a very old Cadillac gage, and using a Bestest indicator both agree.
The Trimos of off .0005 in 6 inches. Not good enough for work but ok for my home shop. It reads .0005 increments so it could be a few either side.

I was previously using my Starrett vernier height gage to hold the indicator, sot this is an improvement.

The base is has a flat perimeter and I think 3 point contact like the B&S stand at work is better.

Dave