What is My Rolex worth ?

[xeroid]

In Canada ... got a Rolex as a gift at work 1989 .... was a copier technician and wore it for a couple of months when the crystal top fell off and I lost it. I put the watch back in it's original box and never looked at it again. Oyster perpetual air king date ,,,, all silver. All original paper work and watch is still working perfectly ( no glass top ). I opened the box after this many years and the second hand is ticking away perfectly. Face may be a little tarnished? Have no idea what it is worth .. Can someone let me know?