Unknown 6 pounder headstamp


#1

So gents today I bought this 57x441 casing (6 pounder) because I didn’t recognize the headstamp… It’s two 5s at 12 and 6 o’clock.


#2

Two serif font " 5 "s and a primer adapter, hopefully that rings a bell with someone.
Serif%20''%205%20''%20on%206%20Pdr%20Headstamp


#3

no-one? starting to feel special :))


#4

The primer pocket & thread arrangement looks very unusual.
Most likely this is something non-standard or an unfinished case or so.
Hard to ID then.