Not bad at all for five pounds, congratulations!
These are German 7.92x57mm cartridges and the 'GM' coded ones are from Messingwerke Goggel, in Moosach. They appear to be in relatively good shape, too.
Well done, no complaints for a fiver! Leon.
"Always do sober what you said you'd do drunk. That will teach you to keep your mouth shut." Ernest Hemingway
There's a second one I need to go back and get for the same price! Didn't realise they were German, but thinking about it there are no crow's feet anywhere. Thanks for the good news.