the paul reed smith bass 4 began production earlier than 1990,it was the early to mid eighties.I won guitar player magazine's giveaway for sept.1986 and the prize was a prs bass 4 and it is still in my possession,it has a dark pearl blue color with stainless steel hardward the bridge is chrome plated brass and there are abalone moon inlays position markers,it has a rotating five way pickup selector knob and a phase switch. you can confirm by reading a copy of guitar player from dec.1986 with Billy Sheehan on the cover (they're all over ebay).