My '88 post (Strong/OEM) measures about 27.05 front to back, but about 27.2 left-right! It varies at various heights. I might remove it tonight and see if it has a size stamped on it.
I removed all the original decals except the chain stay American flag with the script, "designed in the USA" but I recall it said made in Taiwan.
edit: I pulled it, and internal markings are mostly now obliterated by twist marks. I can make out part of the logo and a min. insertion mark, no diameter seen now. By measurement, I would probably call this a 27.2, although it's not very round. Similarly, the seat tube itself is not so uniform, either.
Last edited by Litespeedlouie; 10-11-19 at 09:35 PM.