Thanks, 2Air.
Now, if I could only find Luis H (who has measured two tanks) and enter a little mutual cooperation with him, when I get my tank in for measuring. (Won't need a hydro for another year+, so I'm not running out the door.)
That would make three tanks, and if we had a properly documented way to carve that in stone...any other fossils with these tanks could benefit from it.
Try sending Luis a PM.
In the meantime, have a look at the PST document found here Manufacturers' Documents
It may have your cylinder listed. My old steel 72s are. There is an unfortunate but obvious typo for that model that makes some testers wary.