A member has kindly offered me an incomplete bolt. I can make the missing parts. Fortunately I had not annealed my Israeli 7.92 bolt and started the machining.
Interestingly, the barrel is marked for a Remington 521T, .22S, L, and LR. The way in which it was fitted to the receiver is creative. The .22 barrel is pinned to a bushing. Maybe the bushing was made from the original barrel. The military rear sight is installed on a collar, the .22 barrel being too small in diameter.
The bore in this rifle is a bit ho-hum. Once I get the bolt working, I'll test it for accuracy, and if lacking, I will dip into my tiny hoard of liners. I have a NOS 513T barrel that I may consider installing, but it is larger in diameter, and would require lathe work to fit the forend and bands. Using the liner would be easier and faster and performance should be satisfactory. Also I have other plans for the 513T barrel.