Jani:
If you could oblige me with some pics of the "double duck" stamp, I'd like to add it to my list. With what you've described and the following pic, it appears the "double duck" stamp either lies with Merco or with one of there forge sources. It may just be that Oskar Merkel used the "double duck" stamp-floorplate of the following:







from Cabelas: http://www.cabelas.com/gun-inventory---glendale---merkel---1233166-mer860rs.shtml

So there are a few unknowns. The BBF just might have been sourced from Merco, or E. Schmidt & Habermann or Greifeldt sourced the same "double duck" forge. I'll transmit a few inquires and see if I can get a consensus on the "double duck".

Carl Stiegele of München Höf-Gewehrfabrik sourced Merco(Oskar Merkel) for example #3604 with a Miller single trigger.

I'll have to look a bit later but I think the Berlin branch was at Oscar Geyger's retail shop. So I'd say that the Berlin branch of Sauer at Oscar Geyger's retail shop had an order which was transmitted to Sauer for a specific example and then Sauer sourced Merco.

A Oscar Geyger peddled Oskar Merkel: (copy & paste) http://oldhuntingguns.com/Details.155.0.html?&no_cache=1&L=1&tx_fwwcat_pi1[showUid]=111