Here is an example of a nicely printed "stamp on stamp" from Germany. It is Scott #1008, issued September 4th, 1969. It was lithograph printed with a raised embossed replica of the Bavarian 3 Kreuzer stamp. What makes it relatively rare is the "feel" of the stamp. It is on heavy paper and the embossed portion is raised significantly enough that you can see and feel it. It's 2008 value is only .35/.20.
It was issued on the occasion of the 23rd meeting of the Federation of German Philatelists, the 70th annual Philatelist's Day, and the philatelic exhibit "120 Years of Bavarian Stamps."