On Saturday, February 3, 2018 at 6:36:55 PM UTC-5, Charles Longley wrote:
Well it’s not DIN 965. That’s pretty much what you find in a hardware store.

Could they be DIN 7991 or ISO 10642? These are hex-insert type and not Philips screws. Here is an online source for them in grade 10.9:
https://www.fullerfasteners.com/prod...ersunk-socket/
Uli
'AS'