The Eagle sets sold in the USA had up to ten special stones. The building plan shown below shows all ten of these stones very clearly. These KK stones are of standard dimensions, but have a pattern impressed on one side. The European Eagle sets (Adler) used a number of different embossed stones. I do not know these sets well enough to comment on the special stones. Brian Martinson, Fremont, CA, is the most knowledgeable American Anchor friend and has the best collection of USA Eagle sets; AV Gerhart Bruckmann, Wien, has the most European sets.