The washer appears to be one of the last of the belt drives
That is very true, however it could have been built late 1981 to late 1986. The standard capacity machines with the interrupted perfs on the tub bottom indicates the last generation of the standard capacity BDs. No U.S. Kenmore domestic machines were made in this configuration, but replacement baskets from FSP had them after-market. Kenmore switched standard/regular capacity machines to the DD platform around the time when these machines came out by fall 1981. Whirlpool however continued to sell these, and seems to have sold quite a few in LA5300, LA5700 models, plus a few others. Kenmore kept making coin-ops in this format into 1987.
The outer tubs are slightly wider than the outer tubs of the previous standard capacity models. They share a common baseplate with the large capacity 1981 and later models, which is why the tub is a bit wider. I don't know if the baskets are larger too, but I suspect so. The dimensional differences are small though.
Gordon