The last NAUSET was made in 1973. Any hull from c.1980 would be a "17" hull, with better engine splash well, the bow "smirk," and other improvements.
If the hull is really a c.1980 and is sound, has no damage, is not filled with extraneous holes, has original gelcoat in excellent condition, has no bottom paint, and has clear HIN and stencil number, it is worth a lot more than a pre-1973 hull that is waterlogged, damaged, filled-will holes, re-painted, bottom-painted, without stencil number and HIN. In other words, the value is all about the hull's true age and condition. My estimate: $100 to $2000.
For more advice on buying a classic Boston Whaler boat, see
BUYING CLASSIC BOSTON WHALERS
http://continuouswave.com/whaler/reference/buying.html