Hello Speedy,
They could indeed be Myford; paint jobs were either grey or green in the recessed faces where those are present.. The larger sizes may well have the tooth count cast in on those faces
They will probably have a 1/8 inch keyway in the bore, or if for the ML4, they may have a pinhole on the boss flanking the bore to hold a drive pin [3/16 inch diameter if memory serves]
Values will vary from perhaps £5 up to £15 for the larger sizes The pressure angle [ not easily checked ] will be 14.5 degrees for Myford compatability.
I hope that helps you
Brian