cda,Stamping would not be a viable option, because of the potential
for cracking the fitting itself. What about spraying each seal with
a UV dye that can only be seen with a UV light source.
Had a scenario years ago in that hooligans were pulling the pins
on portable fire extinguishers and discharging them. After an
incident with a few of the extinguishers having been vandalized,
the commanding officer lined up the troops and ran a UV light over
some hands, ..voila! Some of the troops in the battalion were
immediately busted! D`OH !
See the link.
http://www.blacklightworld.com/Security%20Tracer%20Commercial.htm
You may or may not be able to identify the culprits, but with
some good documentation, you might be able to reclaim them
from the scrap yard.
.