Not so much a single coin, but three simultaneously. I'm from the UK and our pre-1947 10p and 5p coins had a much higher silver content. This made them much more valuable than their face value.

They are quite rare to find in the wild anymore, but somehow by the end of the day I ended up with three of them!

Even though the value only totaled about £30 at the time, it was still more than I started the day with.

I'very kept them as good luck charms of sorts.