The two-letter reference dates it from early nineties or earlier. He may have bought it later tho. The movement is a Cal 17, actually an ETA 2894-2 which is a pretty good movement.
If it hasn't been before, it's certainly time for a service. One downside to the Cal 17 is that it's a modular chronograph; this means the chronograph portion sits on top of an ETA 2892-2 movement. The movement is easily serviced but the module can only be replaced. You'll pretty much have to send it to TAG for service and that's pricey (for the module replacement as well as being TAG). The upside is that they command a decent price even today, maybe $2500 - $3000. Service won't be that much.
Here's a much more modern Link Chrono with the same movement:
And no points taken away for being TAG, this is the "General Discussion" forum.
