It's a No4 Mk1*, a simplified version of the Mo4 Mk1 (
no star) Dated from 1942 its a very early one as they started making the non simplified ones about that time. It was originally chambered in .303 British, but many were re-chambered so have a smith check. 30-06 is impossible as the case is longer than the action. Some "American Enfields" ( a totally different design) were chambered in 30-06 so that may be what the seller was thinking.
"U.S. PROPERTY" mark indicates it was slated for the U.K. under lease/lend.
Does the bolt serial number (on the rear face of the bolt handle) match the serial number from the wrist? This is important as they were individually fitted.
Bolt head looks normal for a .303, possibly polished to remove the "ring" that many develop from primer leaks, but you should have the headspace checked if you're in doubt.
Correct head spacing is 0.074" or less, don't get carried away by the hype & rumors, which will come into any Enfield headspace discussion.
Safety can easily be installed, but there is only 1 correct start position when assembling. Its a multi-start thread so there are 6 "wrong" ones, but it feels like 600 when you're putting it together.
Is there an import mark?
"ENGLAND', or a longer one with an importer's name & town?
Incidentally (& pedantically) its not a SMLE. That was the earlier nomenclature for the No1 rifles, this is the later version so to be "correct" you'd call it a "numbah four"