What years was this style of speed limit sign being posted in the good ol' U.S. and A. nation?
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi43.tinypic.com%2F30ic8so.jpg&hash=03b51704cbd9e5c8332ba348c84bd2a7d3bbd92f)
That photo is in suburban Cincinnati.
(Also, that photo is stored on TinyPic, so if it's replaced with something completely irrelevant by the time you read this because TinyPic constantly removes photos and recycles URL's, that's why.)
Hard to say, but I'd date it around the 50s or so. Definitely after 1948, since that's when the current FHWA fonts were put into use, but obviously it's early enough that it was still embossed.
I would have guessed the 1950s. I thought the 1961 standard is what most speed limit signs today use. I thought the 1948 standard had smaller numerals (but you still see some of those occasionally). I used to see this style in different municipalities growing up, so it must not have been too uncommon.
That's a good question, I'd say 1959-ish, somewhere between WWII and 1960.