There are hidden coins to find to get the 45 required. A map by Friar Tuck is available in the download of the game which gives you hints on how to find them.
The Saracen has three sings to sell, so when you get that ring, you will have completed 100% - It takes getting every single coin in the game.
We respect you fully as a gamer and fellow c64 enthusiasts without reaching 100%! :) - We added that for those rare individuals who loves that kind of thing :)