Yeah, it's a sheave gage....
>sheave gauge is boring
Well, yes, elevator cable that works is boring, elevator cable that fails tho....
>"most in need of sheave gauge"
Several in fact ;P
The more interesting thing about it is mostly that it is Roebling's gage...
Stray factoid, the Washburn & Moen standard wire guagem (for steel wire), was in fact, the Roebling wire guage...