"...crown GR..." Kings crown, George Rex for King George V.
"...Enfield..." Where it was made. Makes it English made. No.1's were not made in Canada.
"...1918..." When.
"...SMLE III*..." Model and Mark. The '*' indicates a minor modification that wasn't enough of a change to warrant another Mark. A non-windage adjustable rear sight, et al. Mostly for easier manufacturing or discontinued features like the mag cut off. Even up to and into W.W. I, Brit Generals expected the troopies to use the rifle as a single shot, saving the mag for emergencies. They thought they'd waste ammo if they could.
"...GTR..." Are you sure that 'G' is a 'G' and not an 'F'?
FTR means Factory Through Repair. Means it was factory rebuilt at some time. Possibly in England or India. Check the headspace before you shoot it anyway.
"...RSAF..." Royal Small Arms Factory at Enfield, England. Until W.W. I that's were they were all made.