I don't have an incredibly valuable coin in my collection, but I have 503 coins and if I were to value them all, the collection would be worth quite a lot altogether. I do have a gold gilt 1900 GEF farthing which I am proud of though, and an UNC farthing of 1901. Oh yeah, and I do have a nice 1883 halfcrown in EF, worth £100 according to Spink 2003, and £90 according to Coin Yearbook 2004(I am wondering how accurate Coin Yearbook is!  ), but someone has used it as a brooch in the past, so I am unsure of it's value. There is a picture of it here: