Its not an ST-15... I had one of those and there are some differences.
Its either duratrax Maximum ST or Maximum MT. Could be the Pro version but im not sure...
Here ya go:
http://www.rctech.net/forum/nitro-of...t-pro-rtr.html
Edit- Actually I think yours IS the pro version... Looks like it has the 2 speed bell and spur setup. Kinda like a before its time Jato