Ex workshop spare parts drawers ... the business has closed down (retired "so they say" but I seem busier than ever before!) and all of these small components need new workshops to live in
SQ - XLR Connector
Country of origin is completely unknown
Same goes for the manufacturer, I don't recall running across logo before

Ex stage audio equipment which was manufactured in USA
Type: 3 pin chassis mounting male socket
Non locking and no lock ring thread
All metal construction
Silver plated contact areas (based on the oxide lifted off when cleaning up the contact pins)
Silver Chrome like finish
DIMENSIONS:
Round
Single hole mounting 19.5 OD thread
Flange (that sits on the panel or chassis) 21.90mm OD
Secured with a single large metal nut
Very small Philips head screw holds the insert inside the body, easy to remove for cleaning.
COSMETIC CONDITION:
USED
Clean
NO oxidisation or tarnishing of the body or Silver plated terminals
Supplied in a sealed clear plastic packet