Here is the original patent version:


Here is the modified version:


You can see the date on rib of the modified version is 1892. Here is the original patent:
http://www.google.com/patents?vid=USPAT2...er+1881#PPP2,M1
If he filed a another patent for the modified version, I can not locate it.

I have English and German Pieper reprints of catalogs. There were apparently grades within the Diana grade. The difference is the coverage of engraving and amount of gold inlay. Neither of the guns pictures are on the high end of those grades. Both of the examples pictured above show laminated tubes. The English catalog says the tubes are of Krupp's finest fluid compressed steel.

Pete