I have one of these rifles, a gift last year from my range partner of many years; he knew he would not make it through the Winter and back out to the range this Summer.
My rifle is a beautiful semi-custom but, like yours, the metal work was done carefully and meticulously by the folks at Birmingham Small Arms in England. It has a lovely oil-finish replacement stock with the white-line spacers which were just coming into vogue 50 years ago, an altered bolt-handle, the action is ground and fitted for a scope. It wears a 1959 or 1960 steel-tube Weaver K-4 on low-mount Weaver rings and it shoots well under an inch at 100 when I can hold it.
The bases are a Number 35 on the front, a Number 36 at the rear.
These are a high-quality rifle and they have high-quality barrels on them: 5 grooves, left-hand twist, 1 turn in 10 inches. The rifling is of the Enfield type (5 grooves and 5 lands, lands and grooves of equal with) and is very much of the same pattern as the modern 5R rifling. This twist stabilises bullets in the 150-grain to 220-grain weights perfectly. These rifles have taken a LOT of game over the years and they will continue to do so for the foreseeable future: Enfield-rifled barrels, when used with modern low-temperature powders, have an extremely long life. These barrels also will shoot their best with flat-based bullets. If you are buying ammo, that means don't bother with the premium stuff: the cheap stuff is just fine.
Most common single reason why one of these rifles won't shoot well is very simple: Loose Screws. My rifle was sold off because it couldn't shoot well enough to hit anything at 50 yards. Just another old POS BSA-Bubba army rifle. We tightened the rear action screw 2-1/2 turns and the front screw 1-1/4 turns and it started shooting sub-MOA. THEN I started handloading for it. It's good now.
Clean up your gift rifle, put on a scope which is GOOD ENOUGH for it, handload for it and, with just a little bit of care, YOU will be shooting sub-MOA groups out of your very own 93-year-old rifle.
Hope this helps.