Guys really have to learn which is which if they are playing with Lee-Enfields especially.
Couple of examples:
No 1 Mark 5 (actually V) was a very rare experimental, built only in 2 small lots in 1922 and 1924, although there exist a very few with a 1923 date; Number 5 Mark 1 was the "Jungle Carbine".
Same way, the SMLE Mark I*** LOOKS like a Mark III* but actually the I*** rifles are 1901-to-end-of-January 1907 rifles which have been back to the factory 1, 2 or even 3 times for modifications to bring them up-to-date. There are several variants (I have 2) and they are quite rare. Actual Mark III*, on the other hand, was built in the millions, but only from 1916 onwards.
Also there is a Number 1 Mark IV and a Number 4 Mark 1. My Number 1 Mark IV was built 1897 as a Long rifle, rebuilt 1908 as a Short rifle, rebuilt again in 1942 with all 3 dates on it! The Number 4 Mark 1 and 1* are Second World War rifles, made new in England (3 factories: Shirley, Fazakerley and Maltby), the USA (Savage) and Canada (Long Branch) during and after the war, a few after the war by Pakistan Ordnance Factory in Wah Cantt.
We really have to be on top iof these things so we know what we are talking about.
A NUMBER designates a WHOLE NEW RIFLE. A MARK designates a variant of an EXISTING type and a STAR (*) gives a relatively-MINOR change which is not worth a whole MARK.
When the new nomenclature system was developed in 1926 and introduced in 1927, it went like this:
ALL Lee-Metford and (Long) Magazine Lee-Enfield Rifles retained their original names..... and became obsolete, as did their respective Carbines.
Number 1 was the SHORT rifle, the actual SMLE rifle in calibre .303". The many various Marks and Stars were retained.
Number 2 was the .22RF version of a Number 1
Number 3 was the Pattern of 1914
Number 4 was the new rifle originally developed as the Number 1 Mark VI, then changed to Number 4 Rifle at the same time as all screw threads were changed from Enfield to BA. Buttplate screws and front-sight blades SHOULD interchange between Number 1 and Number 4, but that's about all! (Actually, the 2 internal action springs, Extractors, Stock Bolts and Washers can be persuaded to work.)
Number 5 was the Jungle Carbine, although most Number 4 parts will fit it.
Number 6 was the Australian Jungle Rifle built on the Number 1 frame; our chances of owning a real one are pretty thin.
Number 7 was the .22 version of the Number 4. There are at least 3 variants of these: the British version, the Long Branch .22" and the C Number 7.
Number 8 is the British Cadet version of the Lee-Enfield
Number 9 was the sweetest assault rifle ever designed, the EM-2 selective-fire Janson rifle in .280/.30. Rifle, cartridge and number all disappeared under massive US pressure, although US "state of the art" ammunition developments are coming close to catching up with this British 1949 design.
The entire system was washed-away by the development of the newer L (Land) system of nomenclature in Britain and by the C system here and R system in South Africa.
Hope this diatribe helps somebody, at least......