The North American Vexillological Association visited that flagmaker during our annual meeting ca 1995 and I recognized that type of stiff muslin material. They gave me, gratis, a number of obsolete foreign national flags they still had "in stock" that dated back to the 1950's - could have been printed the week before, or in 1955 - impossible to tell. You may see them at my flickr.com link below.

How long do you think those flags need to be left outside, exposed to the elements, before they become "antiques?"

Nick