Some of the ‘80s solid bodies used very thin trapezoidal TRCs like those:I think that was a rare case where due to the angle of the headstock and the thickness of the neck the opening for the truss rod was going all the way to the nut and there was no way for a center screw.
New Hartford made bass, same same:
The Newark St. Starfire II has the same issue:
A few 1980's Guilds also used 3 screws at the bottom as this picture from @Knash shows: (I leave it to others to find out which models used those two...)
Ralf
It is "F-30 Rosewood Paul Simon". They were especially made for Japan, one had the blue export label claimed to be from 1981 or 1982. Dots on fingerboard, not stars. 15 1/2" wide, 4 7/8" deep. Somebody else in Japan claimed he had one from 1985. The 1982 Japan catalog did not show this specific model, but the 1982 pricelist showed a special model as "F-30RNT" and the line behind the Star said:What's an F-30RPS, Ralf? Any idea?