i think you got a good deal on that, have the same bow (except in right hand and 60# draw weight) and i love it, and they are definately fast shooin bows, and id guess that its a mid nintys bow like bonebuster said, like you i am the second owner of the mamba tho so i cant really help much with the age.
just a word of warnin tho the stabilizer screw (cant remember the name) had glue problems on mine so my stabilizer falls out could just be my bow tho and it is a easy fix just too lazy to do it tho