Was looking at a crystal: round holder, Blilely,
has serial number stamped, and frequency 3625.
It has a "safety wire" securing the holder screws.
The safety wire is terminated in a lead seal, stamped
"SC 28". The side of the holder has red stamps,
"SC 28 A" and
"MODIFIE_
PSD"
Any clues? Tnx - Hue Miller