I've had '60s cardigans with suede patches and had the same dilemma, but my feeling is that to survive this long it's likely that they were washed and indeed I have hand washed them and they've been fine. I wonder if the suede is treated with some product?
A few years ago I had a disaster at the dry cleaner - they had washed one of my suede '60s vests and it was a mess. Lost its shape and the dye ran all over the place. They compensated me for it, but that's how I learnt that they sometimes wash things, rather than dry clean them. They must have considered it to be a washable material. Bizarre.
Yesterday a lady came in with a polyester late '60s wedding dress with some marks. A dry cleaner had quoted her $500 to get them out. I told her to wash it on the gentle cycle - I'm sure they were going to wash it too, I can't see that the dry cleaner would get these out but I'm confident that a good old fashioned wash would.