Unless it has been kept in pristine condition by someone who knows how to do it, I'd advise him to pass on the really older 1100's. Production started in '63, that's old! (I was born in '63...) My Dad has his he bought in '64, and it still works fine. I got to use it's sister gun he bought later (@1975) for Trap, and had to constantly work on it. It had been abused before he got it, got a bargain on it. That gun is actually responsible for my learning to gunsmith-i had to to keep it working. Problem is, most of the older 1100's out there either were abused, or sat in a closet for 40 years. The latter still need a good cleaning, but you need to be able to tell the difference.
I have less experience with the 11-87, most of the ones I've seen were fine. The ones to avoid there are the ones with Duck Camo painted or stuck on; they've often seen some hard use.