I wouldn't spend very much for it, maybe less than $50. I have a 6160B and I will tell you my experience with it. First of all, the amplitude range is only 3 to 13 dBm, meaning if that you want to use it as an RF signal generator, you will probably need an external attenuator. Secondly, my unit had the ovenized oscillator option and I would be wary of the stability without that option.
But the real problem is the serviceability. You will need a graduate degree in test equipment repair to successfully restore a 6160B. The modules are all contained in sealed boxes and you will need several SMB cables and a lot of jumper wires to be able to remove a module, open it up, and hook it back up so that you can work on it while the unit is running. Moreover, Fluke designed this thing with many hand-selected varactors and a ton of inductors. At one point, I attempted to adjust an inductor and it crumbled into dust. I ended up buying a second unit (for $20) and with a lot of trial and error, managed to combine the two sets of modules into one working unit.
And then there's the "main" board that I needed to remove which had a 34-conductor cable soldered to it. Why Fluke didn't use a connector is beyond me. Not fun unsoldering and soldering the cable. And alignment? Forget about it.
When I finally got everything to work, the 6160B is not a bad synthesizer. Maybe it was a marvel back in 1973, but I'm not impressed.