Congratulations and welcome aboard. You snagged a very rare model. There are none listed in the "our C Dorys" that I could find.
Here are a couple of the brochures: 21 offshore:
The factory hard top version is the Pro Angler 21:
I would not be afraid to go to Catalina, or other Channel Islands in. S. Calif; In San Francisco Bay--or out to the Farallons on a calm day. I don't know if the 21's are self bailing or not--and how tight the fish holds are. So be sure and have a couple of good bilge pumps, in case the weather picks up. Of. course the usual safety gear, including good life jackets, at least one good VHF 25 watt radio, an EPRIB or PLB, appropriate cold water gear etc.
The hull has a substantial greater V than the 22's (12* for the 21, about 3* for the 22's), so will handle the chop better, yet by modern standards, it is still a low dead rise boat.
Here is a
link to some further discussion:
A little more digging, C Moss, was owned for about 3 years by an active C Brat. She was sold in 89 new as a semi custom boat. Her serial number of 5 suggests that there were at least 5 built on the 20' hull. There is at least one open one, which Harvey has spotted in the Port Angeles area. Several of the hard top version have been mentioned. The mount of the engine seems to vary some. Power was up to 140 hp--so those boats probably rode well when in the mid to upper 30 mph range. Interesting that more were not made. Wonder what happened to the molds? Probably did not survive to the Reynolds (2002) era, or it would have been ideal for the center console model.