I've seen this designation applied to Darnes on the different gun-list sites over the years. Sometimes the gun is clearly an R10, and I sort of assumed they were the same thing. Gunbroker has an small-key Darne listed as a "Type 10," and it's clearly not an R10 http://www.gunbroker.com/Item/618729254 . It has quite a bit of engraving but lacks the chisseled fences of higher-end R or V model Darnes. The stock also differs from the R-series in lacking the oval carvings in the wood below and in front of the receiver. This stock more similar to the Darne Halifax. Based on the serial # 3PXXX this looks like a pre-War gun.

A search of Naturabuy.fr turned up a few Type 10 Darnes.
http://www.naturabuy.fr/Fusils-Juxtaposes-Darne-Type-10-critere-581628.html
They're all selling for well under the $2K+ opening bid on Gunbroker!

Anyone have any experience with this model?

Bill