I can't read the number under the M5, but it looks like a 9. These would be correct for 1970 B- and E-body by date, and also found on 1971 models. These are hard to find, especially in this condition. The last set I had was from a 1970 RR, and as nice as yours, but factory purple and all four dated within a few days of each other. I got $750 for the four of them, and that was several years ago.
Yes, it’s a 9 under the M. They really selling like that? Dang. Guess I gotta get back into stock parts like wheels again if that’s the case. I remember taking matching sets to Dick (rip) at Stockton Wheel for $10ea for cores and he’s cut the centers out and make them 15X8 for $90 bucks back in the old days. 😭
