The letter O is missed out because of a possible confusion with zero, while Q also leads to confusion when stamped very small. The reason is that the Italian language does not use the full alphabet – J,K,W,X and Y are not used in Italian words. You may wonder why the letter sequence is not logical. Other Blue Book publications - Blue Book of Black Powder Values, Blue Book of Air Guns, etc.
Probably the most widely used price guide. Blue Book of Gun Values by Fjestad, uses the percentage system, good for modern guns, no pictures. Here's the list - and apologies for a rather long post: Italian guns are easily dated by a code - not in the serial numbers but next to the proof mark.
