Great Britain Old Stamp

hello!  thanks for your positng.  I am afraid that your stamp does not have an established error, but rather the stamp that was sliced below it would be considered to have a serious "fault."  There are tons of variations of this stamp, but generally speaking it is worth about $2 full retail, but you can purchase them all day long on ebay for less than a dollar (plus shipping :-)) - it is a beautiful stamp to look at I think -- thanks again!