1950s to 60s
Made in USA
Deadstock - New Old Stock, still pinned to cardboard and has cardboard under the collar.
RN # indicates Riverside Shirt & Underwear Co of New York
Size Medium Long Tail. I have not unpinned this to measure, but at the same time I acquired this I got another one (also a Medium) that was NOS except it was not still pinned to cardboard.
The measurements on it are as follows:
Length to of shoulder to hem: 28"