Good article.
Explains the difference in the first SMLE,,The MkI and the quick changes made to it that were then adopted as the MkI*.
These have the Sliding Charger Guide mounted on the bolt head.
Only made for a few yrs, the MkI* is the more common variation you may see. But they are very rare by any count.

The common SMLE most people think of and have is the MkIII(*) with the solid one piece charger guide rivited to the reciver.
That came out in 1907.
MkI* rifles updated to MkIII SMLE's were remarked as MkI***

(Yes there is an SMLE MkI**,,it's a designation set aside for the Ishapor Arsenal (India) mfg'rd SMLE that followed the MkI* pattern.)

The SMLE didn't become the Rifle 'No 1' till mid 1920's when the Govt decided to assign numbers to their infantry rifles.
SMLE #1
SMLE .22 trainer #2
Pat 14 Enfield .303 Rifle #3

Later
Enfield .303 Rifle #4
(Jungle)Carbine #5