That is a FN Model A 22 lr (Browning SA22).
The "Model A" might still be visible on the top of the box.
The rounded pistol grip may indicate 1920's (along with the "smoke less powder" marking on the barrel).
The serial number, if original to the gun suggests it would be a 1956 or 1957 model, but (to me) the pistol grip looks wrong to be that (late). Before 56 serial numbers weren't required and there are no records from FN.
I can't see for sure, but this looks to be the "top loader" style.
Sorry, can't help you with a value - a 22 short version recently sold in the US for $440 (similar year range to yours by the look of it).