With most .22 rifles, you make sure the rifle is EMPTY, then pull the trigger back to release the bolt. Pull it again to slide the bolt back in. Some rifles use the Mauser-style bolt stop on the left side of the receiver.
Looks to be a Savage Model Sporter 23A. Here's a link to a gunbroker auction of one that looks just like it.
Actually other than the schnabel fore end it looks nothing like it. It looks to be a Mauser to me but I know next to nothing about .22 Mausers. It should be marked on the receiver if it is indeed a Mauser and the safety would be at the rear of the bolt. The pics aren't clear enough to tell if it has the Mauser style bolt release.
The semi bull barrel has an interesting taper to it and the whole rifle says German Garden rifle, although most are single shots. Better pics of the action would help, and appears there is an screw/ bedding screw? missing. Does it shoot well? Good luck.
I daresay it's a BRNO model 1 that has been shot to pieces and rebarrelled with a new Shilen heavy barrel. I'm pretty sure the lever locks the bolt, you flip it around to the right when the rifle is cocked and it will prevent the bolt from dropping when the trigger is pulled.
If that rifle doesn't shoot well there's something wrong, between the Shilen barrel and the (CZ) BRNO name, it should be capable of MOA and under at 75 metres at least. BRNO rifles are legendary in Aus for their accuracy and reliability.
Rab, you are a Smar Tazz, Offensive reply to my trying to help you, so Never will I ever help you, or read your posts.
I am an Master Machinist and gunsmith specializing in FN FAL, AR's,and other tactical and SPR's.