In addition Greg Gagliano sent me the Rivera-era-relevant numbers from his huge research info, for which, along with his friendly encouragement over several years, I thank him.
His info (he rightly didn't include details of the amps' owners) still represents about a sixth of my database.
Eventually, I thought, I'll get a rough idea what the highest and lowest s/ns were.
Subtract one from the other and I'll have a rough-cut figure for how many were made. PRII owners were kind enough to start sending their serial numbers in.
Then the terrible truth dawned on me: they WERE all mixed up; Fender had decided to change their 35-year-old system of serial numbering so that, starting in 1982, every amp had a unique number.