5' 6+", 54 CM classic frame. I bought the frame in 1981, and it fit perfectly; now it's a little big, but not so big that I need to replace it.
There are at least 2 ways to measure seat tubes - center-top and center the center of the top tube or virtual TT. A frame measured 53 CTC will probably be a bit (less than one CM) taller than a 54 CTT. If you're interested in standover, ST angle has an effect. A slacker angle will have a lower TT.