Can you help me identify my bike please? Bought this bike off a friend, but it has been repainted and I am just curious as to what kind of bike it is. 

Seat, and both tires are not stock. I have replaced all of those since I bought it. 

Any ideas would be appreciated. I have been researching the serial number hoping that I may find something. But haven’t. In case that makes any difference the SN is rcy10010578
Firestone mb3 mountain bike aluminum