Those cabinets look to be late-'80s vintage, IIRC.
That actually, looks to be a 4.5" or 5" woofer. I have several sizes of 4" through 5.5" surrounds; however, I need fairly exact measurements of the outer diameter of the cone PLUS the outer diameter of the basket, to determine the CORRECT surround, of a driver in this size range. Simply TOO MANY different increments of size, to do by "eyeballing" it...
Regards,
Gordon.