I think it's likely WWII...a lot of WWII sweetheart jewelry utilized old model EGA's...my question is what the heck kind of lingerie did it clasp? Very interesting
If you look at the patent, it was like a strap clip for undergarments (lingerie). It looked like it would keep multiple straps together right below the front of the shoulder. The company closed in 1922, so I don't think someone would take old stock of lingerie clasp to make WWII items. There were later patents by other companies for lingerie garments in the 30s and they were being made of plastic. It is definitely an odd combination, if it could only talk...
What is the date range for the EGA?