Those are the old T156 "angle block" treads found on the 105mm M1 and M1IP series M1 tanks; the newer variants from the late 80's to earlier 90's switched patterns over to the "square block" T158 track patterns...
That's the newer tread on the M1 tanks I believe... The early 80's M1 and M1IP tanks had T156 treads, those look like the T158 early to mid 90's pattern...