OMG! That is the same bass I have, only mine is in blonde. $150 for that is an absolute steal. I would have snagged it myself in a heartbeat had I seen it. I don't recall the original price because I traded two other basses, plus some cash for it in a music store in Madison, WI.
Here is mine. I bought mine in 1981 too. I haven't played much in recent years due to family, career, etc. so it has very little wear, just like yours. Congrats on your snag and if you decide to dump it, let me know.
Also, read this link for more info on the old Washburn basses. ATTN WASHBURN MEMBERS--SB40 History