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" (there were no stickers on this one to indicate Long Tail)