Here's info on the RT500. The parent website doesn't list an RT550 for 1994.

http://www.bikepedia.com/QuickBike/B...T500&Type=bike

Raleigh bonded aluminum frames were generally very well constructed, despite the knock bonded frames get. Looks like it was a mid-level offering. Unless it's been abused, I'd say it's worth building up. I wouldn't dump enormous amounts of money into it, although you can always migrate the components to a different frame later.