If the 16 refers to the number of gears grab it!

If the 600 is dark anodized, and it is 8 speed cluster, it is the 600/Ultegra and is a very nice group, and is probably on a nice frame too. Probably has Dual Pivot brakes (my 1989 Centurion with a 7 speed cluster came with single pivots, but I think the next version would be dual pivot.

I spent $115 on mine... and it is the 7 speed cluster. Actually, does it have brifters? If so that boosts the value as well.