It's in the orientation of the strings; in the 4008, the octave strings are on top, whereas on the 4003S/8, they are on the bottom.
However, the bass models article states that the 4008 was discontinued in 1983, and the 4003S/8 was introduced in 1987 - obviously, this one falls between the cracks! It might be worth e-mailing the serial number to RIC service and have them check to see what the model designation was.
That's a mighty fine bass, congrats!
It is better, of course, to know useless things than to know nothing. - Seneca