Can anyone help me to identify my TREK mountain bike model from the serial number?

I bought my TREK mountain bike in 1999 when I was living in Germany.
After a few years of use I moved & it kind of got mothballed for the past 15 years for one reason or another.
I am now back on the road and its pretty much like new after some basic maintenance.

My query is what model is it (receipt is long gone). Info that may help:

• Serial number is: S99050362 (nothing on the http://www.vintage-trek.com/ looks relevant)
• 27 Shimano gears with Deore LX M570 STi shifters;
  ( Silver with black decals colour; fairly light weight metal (aluminium??) frame.

It may be a model manufactured from about 1996 onwards but I bought it in late 1999.
Any insight would be appreciated.
I have trawled the web but the serial number on the frame has no hits.