Hello again. I posted my last reply just before I saw the additional photos. Think you and I posted almost the same moment?
The Barrel: I just noticed the single hole rear sight on the barrel. That shape/style is very much Turkish or Persian. Could be the origin of the barrel?
Barrel Tang Screw: I now see what you mean. You can file down the burr on the top near the tang. Then remove that small pin at the lower end near the sling swivel. You should then be able to remove the barrel screw from the bottom. The barrel tang and screw can have new threads made later. (I'm assuming you want to remove the barrel). Most Afgan rifles I've seen have fairly thick barrel bands. To get the rear bands off you will probably have to remove the forward sling swival. Instead of a screw attachment, most have a pin and brace assembly. Yet another pin
That will have to be cut off on one end. (The pin can have threads added later if you want). If the barrel bands won't slide off by hand, a smaller hammer and a wooden dowel will usually work.
The Lock: The lock looks very much like a locally made one. Maybe "copied" from the Baker pattern?
Keep me posted on your progress. Rick.