Since I posted this I got an email from Alf on AR. It is not a CZ but an action made by BSA. The chamber and locking lug recess is in the barrel and it does not have the third locking lug like the Mauser but relys on the bolt handle. It was probably designed by Otagar Galas who designed the BRNO ZG47. The muzzle brake is original to the rifle, very unique for 50 years ago, but as lv2 states, a useless addition. By the way the rifle weighs 6 pounds so maybe it is not useless.

Alf says $400 tops for 100%.