That's because you are familiar with machine systems, and it is not a problem for you to spend your time that way. I imagine you own or have access to at least 1 (or more?) surface plates to inspect for flat. Starrett castings are not unknown to warp, though they probably don't wear very rapidly despite slate and chalky cloth being abrasive.
You could probably take a good surface plate to Trent's, a small scraper or 2, some diamond laps to keep them in shape, a tube of hi-spot, maybe something to inspect the surface plate from time to time.....see where this is going....? Then given how fast he learns stuff, probably teach him to touch-up scrape and dial in a level in an afternoon.
OTOH, He's a professional at what he does, maybe he would prefer to use his spare time
Similar looking levels come in a range of sensitivities. 98-'s are aprox 80 - 90 arc sec, or aprox .005"/ft. Castings for frames similar to the 98- under discussion came with vials as sensitive as 10 arc sec/ .00058/ft for special purposes (will drive you nuts/useless on a pool table). Then they made cheaper levels on the same frame with blown but not ground vials, (97- IIRC) for which the sensitivity is outside .005"/ft and ambiguous.
If yours is a ground vial .005"/ft, it can be used alone, or with a scraped parallel of any length(s). Or even a ground parallel. I understand that such gages would not be common in the tool kits of people who aren't machinists. It could work fine to set up your own table. It could be a time killer for a pro to schlep to jobs.
