SMLE stands for Short Magazine, Lee Enfield; less formally, troops called it the "Smellie." The Mark I was adopted in 1902 as the British service rifle following their decidedly unpleasant experiences fighting the Boers, many of whom were using charger-fed 7x57 Mausers, in what we now call South Africa.
It is "Short" because its barrel was shorter and therefore less cumbersome than its predecessors, the Lee-Metford of 1888 and the Lee-Enfield of 1895. The "Magazine" denotes that it could be loaded with two five-round chargers, so it held five more rounds than the Mauser and was much faster to reload than the older Lee-Metfords and Lee-Enfields (their magazines held eight and ten rounds, respectively, but like the US's Krag, the rounds had to be loaded one at a time).
"Lee" commemorates Richard Paris Lee, the Scottish-born American who invented this box magazine system, while "Enfield" refers not to the armory located at Enfield Lock but to the system of rifling with deeper grooves than those used in the Medford system.
With me so far? We've almost finished! The * following the Mark III indicates an official modification of the model pattern, but not one so sweeping as to require a different mark, as in, say, the Mark IV used by the British in WW II (the Australians stayed with the Mark III). The SMLE Mark II's were updated Mark I's; the Mark III was adopted in 1907. The Mark III*, adopted on January 2, 1916, did away with the long-range volley sight and the cut-off for the magazine. In May 1926, Great Britain began a different system of nomenclature: the Mark III* became the Rifle No. 1, Mark III*. If you can keep this straight, you're a better person than I am.
All of these models plus the later Mark IV and Mark V fired the .303 British, a rimmed cartridge introduced with the Lee-Metford in 1888. It was at first loaded with black powder for about 1850 fps, then with smokeless cordite for about 1950 fps, both with a 215 grain round-nosed bullet. In November 1910, the S. A. Ball Cartridge Mark VII became the standard, a smokeless round with a 174 grain spritzer developing about 2450 fps.
In the next post, I'll discuss how I made over a sporterized Mark III* SMLE.