I recently bought a couple of kilograms of mixed coins for £10 - about 600 coins in all. You never know what you're going to find, there's always a lot of dross, British pre decimals, US 1 cents, demonetised European pre-Euro coins etc.
To be honest I mainly buy it for the $, Euro and Swiss Francs currency! But every now and then something a little special appears. When I fished this one out I knew it was silver, as the Swiss used silver for their higher value coins right up to the 60s. The wear is a giveaway as well. But I was stunned when I saw its catalogue value, thanks to a tiny minting of just 50,000 pieces. How many of these have survived, how many have been melted down for their silver content, how many have just been lost over the years?
I've priced this at £75 in various places, but I won't link as the odds are it will sell very quickly. At the moment (14.20 on 12 March 2015) it's still available!
I've fished out a few more Swiss silver coins, but I doubt any will be as valuable as this one ...