It won't exactly be easy, because the components are still affixed to the frame, but if you can get in position to see the reverse side of the front dérailleur cage or rear dérailleur body, wipe it clean, and you will find a two letter code. Not VIA, that's a Japanese standards code for bike parts like UL is to our electrical appliances. Not the model number, like FD-350 or RD-250, etc. A two letter code. Then go here and determine the dates of the components: http://www.vintage-trek.com/component_dates.htm#shimano

That will roughly give you an idea of the model year, assuming the components are original, which I think they are. If the components were manufactured in the last several months of the year, they may have been used on the next model year.

Then, if it is 1993 or later, go here: http://www.airfreetires.com/specs/St...nd=Specialized

You'll find most of the original specs there. If it's older than 1993 I have no idea where you would find original specs, unless you can get that year's Specialized catalogue.

What does the decal say? Hard Rock GX? That might be a clue, too.

Honestly, I wouldn't bother trying to restore it to spec, unless it occupies a special place in your heart. Those components are entry level stuff, and the frame is likely entry level as well. That doesn't mean it won't ride well, it just means it might not be worth the investment. I'd just ride it as is. If stuff starts failing, upgrade those parts with something better, and keep riding. You can't beat free. Some might suggest not spending too much money on that frame (if you can positively identify it), because it may only have chromoly main tubes with high tensile steel forks and stays. What does that mean? It just means it might be a little heavier than it's more expensive contemporaries. Some might think the more expensive bikes ride better, but that's all subjective. If you like it, ride it, upgrade it with modestly priced parts as needed, and enjoy!