On Tuesday, June 9, 2020 at 1:27:45 PM UTC-4, wrote:
A quick way is to only use a TOST ring set where you can still read (most) of the TOST part number stamped on the side of the small ring. With dimension change due to wear&tear, the part number will become unreadable.
This has the dual benefit of also ensuring you are being hooked up with a proper TOST ring set and not a home made or repaired set.
PS- Remind me to take a calipers out to the airfield next visit and validate a suspect worn ring’s dimensions. Thanks, whoever posted the spec dims.

It's on the oval ring on my ring pair... and TOST is stamped at the bottom of it.