I know this may be off topic but I very recently received my father's "coin collection" as he wanted me to have it since he "wasn't going to live forever". We're talking about a senior (me) and a WW2 vet (him) and probably 45 years of sending/sharing coins/notes.
Among all the many things in his collection was a 1958 20 cent coin that represented one of the reasons I had moved from coin collecting to note collecting and then quickly into chartered bank note collecting. It hadn't really increased in value over many years so I had passed it along to my father.
NOW, upon further investigation it turns out this coin is a "Blundered I in VICTORIA" coin and has a catalogue value 4 times purchase price......No wonder collectors like Tom keep an eye out for those "error" notes/coins!
You just never know!
Happy Collecting