First things first - what a gorgeous little girl!
OK, to business. first off, that is one beaut weapon! The finish is superb. On the right (looking from the butt) of the receiver, that ring bracket is the mount for the magazine cut-off, either missing from, or not fitted to this example, This bit of kit allowed a fully loaded magazine (10 rounds) to be retained, and a further round to be chambered, by the bolt, for immediate use on 'Advance to contact' - in other words, retaining full load, but with one extra, when going 'over the top', or into immediate contact.
At the extreme rear of the bolt, the vertical, flat ribbed part is the striker 'grip' of the firing pin which, as you know, runs through the bolt itself, and shows the weapon's 'Registered Number' - serial number - which should be the same as all the other stamped numbers on the receiver, bolt, butt etc. These weapons were literally hand-built, and could be made with 3 different butt-stock lengths, to accommodate the individual.
On top of the receiver, within the bolt housing, you'll notice a vertical slot. This is the 'Bridge Charger Guide', which was designed to accept a 'charger' ( a clip) of five rounds. The chargers were pressed down the guide, immediately loading five rounds into the magazine (which was only removed for cleaning, remaining on the weapon in normal use), allowing very rapid loading of 5 or 10 rounds, with the facility, if needed, of loading individual rounds by feeding independently into the mag. The charger, or clip, was then free and ejected. (normal issue was in chargers of 5 rounds, designed for rapid loading.)
This system, together with the precisely machined bolt and breech assembly, made the Enfield, and it's successors, the fastest. smoothest, bolt-action rifle in the World, a 'title' which has yet to be surpassed.
The 'tunnel' in the brass butt plate is known as the 'Butt trap', and held a cylindrical, brass oil bottle, plus a 'pull through' cord and weight, intended for basic cleaning in the field. The full cleaning kit was carried by the soldier in the front, left pouch of his webbing belt order.
You have a fine example of the gunsmith's craft there RA, a real beaut, and it should be able to put each round within half an inch at 1,000 yards, every time.
Nice one mate!