Paul, when Modelville was located on Speen St.(Rte. 135) in Framingham, there was another Sovereign there, along with an American Orange & Windsor. That was my home raceway from 1969-75. I'm not aware of the Sovereign that was in Randolph. Do you recall the years it was there?
At my age, I have a hard time recalling anything - but, I'm going to guess it was mid 60s maybe? 63-66? I used to wait for hours to get time on one of the lanes of that track.