Please forgive my boyish enthusiasm.
The threepenny bit was nice, but they only went back to 1937. The penny was easily the best. Even at the end you could still find them from as early as 1860 - before that they were made of copper and were much larger. You had the 1918 and 1919 H and KN versions, the 1926 "modified effigy", and the 1902 "low tide" variant to look for. Actually 1926 was quite scarce in any version. The moment triumph when finding any of these - gone forever.
At least I thought so. A few years ago in a secondhand shop, I picked out an Edward VII penny from a tin box, and, glory be, it was a 1902 low tide. All the old excitement came flooding back. I expect I had to pay about 20p for it. I've no idea where it is now, but that doesn't matter - I found it!
Again, please forgive me.