The info referenced in this thread is correct.
http://forums.cadillaclasalleclub.org/index.php?topic=133404.msg285233#msg285233The head-stamps on the bolts such as "TR", "WB",
etc. denoted the manufacturer of the hardware.
There were also unmarked bolts in the mix as well.
There was no attempt to use all of the same
head-stamp when assembling the cars. The line
workers had the bolts in buckets that were filled
as needed with no regard for keeping them all
identical.
The Corvette people have their "Bloomington Gold"
style judging insisting that all the bolt stamps need
to match but that's not how they rolled off the line in
the 50's. My '55 Eldorado had a mix of bolt head-stamps
and that's how it was restored as well.
Mike