This is the 1965 Old London coin. These look very much like the ones that Topps included as inserts the year before. The Old London coins, though are much scarcer. I very rarely see these show up on Ebay and when they do they are very expensive. Right now there is just one listed. Its a PSA 6 and has a BIN of $60.00.
Mine is in really nice condition, too, but I paid just $2.80 for it. I got myself a real bargain.
Here's a look at all 100