HI......that looks to be a 1927/28 BSA standard no2......In fairly average condition for one that has been left unattended for a few years.......It probably works as it is, But as a precaution, you could unscrew the three screws that fix the triggerguard (the front two screw into the triggerblock and prevent rotation)...and, standing the gun upright with the muzzle on something like a piece of carpet on a solid surface, unscrew the back end, the wood and trigger block will come off as one.......you then remove the spring, or springs (may be one long one, or two shorter ones)....then remove the screw which connects the arm which goes into the slot underneath, and take this part off....hook this bit in the piston and withdraw, and check that there are no foreign bodys inside the chamber (old pellets, nails, ball bearings......it DOES happen!).....If the leather washer on the piston is in good order, and the screw is tight, and the spring is not broken, the next thing to do is clean the barrel with a cleaning rod, or small cloth patches pulled through until bright......a bit of grease on the piston and spring, replace all as removed, and the gun will function!

Cosmetically, a light rub with 0000 grade wire wool soaked in oil on all metal surfaces will improve things no end, and you may well get a nice suprise.if he is not happy with that, then a reblue will cost £50-70 pounds.......the stock can be given a wipe with a variety of proprietary oils as you prefer, ccl oil is quite good. The gun looks complete (I cant see the front sight, but the rearsight looks OK, so that is a result!).....does the rear of the stock have an oval bung with two screws present.these are often missing/broken?...this is the access to remove the stock, you will need a large, long screwdriver (or better still, a 3/8 drive socket extension, with flat blade insert)

lots more info on various threads on here..there is a spring gun lubrication one for example, but it depends on what the owners expectations are, a full refurbishment, or a "honest" example, cleaned up and functional, which this gun could easily be made.