In my opinion the "conversion" looks similar to the Civil War Era "conversions" known as the "Belgian Conversion" or "Cone Type Conversion". This is commonly seen in an area where I have substantially more experience collecting, Muskets (Mike I used it correctly this time). It was a common way the Belgian's would convert their Flint's to Percussion, thus the name.
On a side note: I prefer the word "alteration" when discussing the change from Flintlock to Percussion, but do utilize "conversion" myself in conversation because it seems to be widely accepted collecting term. I think I came across an article from Nord Flayderman where he also took issue with the term "conversion", because the actual purpose of the firearm is not being changed, just altered.