CZ 75b, should I buy it?

I just ran across a very used cz 75b. It is old, has some odd aftermarket sites on it, the finish on the frame is turning red, the trigger on it is sweet, has the spur hammer, and it is only $320.

I didn't look to see how old it was, but maybe one of you can help me with that. Its serial number was 80***.

They wouldn't let me pull it apart at the gun shop so I don't know what the internals look like, but there was one thing on the frame that looked kind of odd to me. On the left side of the frame, in that opening just behind the safety there was a set screw that was actually coming all the way out on the same axis as the barrel. I haven't seen anything like that on the newer production models so I thought I should check and see if that is normal.

Thanks for the help guys.

Shut up Brad. I want the opinion of somebody that knows what they're talking about.