What model is it?

[circuit19]

I have a 77 20 or 21' Fiberform and am try'n to figure out what model it is. The tag starts out SF but after that I'm clueless. It has a cabin with a fridge,sink,closet and table that drops down to make a bed big enough for two. There's no seats in the cockpit and a couple of rod holders near the transom. Ive, been try'n to find out just so I'd know exactly what I have.