I can remember that when I first got an air rifle a tin of 500 .177 Eley Wasp (Red Tin) was six shillings (30 pence) at the local iron mongers.
Later on he also started to stock Milbro Caledonian and Bull Dog Pellets these were offered in tins of 500 or 200 or sometimes cardboard boxes.
These tins look very collectable now but back then they made very attractive targets once they were empty
I have never seen tins or boxes of 100, except for the match wadcutters that would have come in square plastic boxes/trays and individually separated by being in foam inserts? And were far too expensive for young boys!