And a belated reply, with a minor update: browsing around the forum for further information on these creatures (I'm now thinking of buying one myself - it's everyone here's fault, I tell you!) I came across
http://blade.japet.com/B-afghan1.htm - which got me thinking about this lock. I had attributed the cut-away section of the lock to a crude attempt at de-activation; is it instead possible that this was a native-made flintlock, modified to become a caplock? I present my hypothesis - with thanks to LPCA - in the form of this magnificent illustration.
I also attach a couple of better pictures, which might show the watering more clearly than did my previous efforts.