I believe SPECIAL grade, meaning all new barrel, stock, etc on a completely refinished GI receiver.
The highest, most expensive grade that was available.
Pretty sure it was this one:
RM1308SPECIAL
CMP Special (.308) M1 Garand. This is a completely refurbished rifle consisting of an original M1 Garand Springfield or HRA receiver, new production Criterion barrel, new production American Walnut stock and handguards, and new web sling. Receiver and most other parts are refinished USGI, but some parts may be new manufacture. Receiver may have pitting. A .308 spacer block is installed to prevent the loading of a .30-06 round into the chamber.