This is an interesting question I received!
First, at the start of WWII we need to remember that the United States (and the world at large) was just coming out of a lengthy depression.
A natural result of that depression was that most men and women of that era were of a fairly uniform size physically. This means that most clothing was pretty much of the same size with the exception of height.
The lack of food, particullarly the kinds of food we enjoy today, kept most peoples weight in the same range. An average man would weigh between 140 and 150 pounds .
What this means is that for most pilots in WWII with an average weight of about 145 pounds the size of their heads would be roughly the same.
During WWI and WWII the American Optical Company manufactured mobile optical units to provide glasses and aviator glasses to American soldiersand pilots.
The original Aviator sunglasses were NOT Ray-Bans but rather American Optical General sunglasses which came in two sizes: 52mm and 58mm.
By far the most common size was 52mm.
Later AO introduced the AO Original Pilot sunglasses with the more rectangular shape. Today, that is the most common style of aviator.
In my business, (Aviator-Sunglasses.net), I sell a lot of replacement sunglasses to some of these older pilots and by and large they choose the 52mm size. I love helping these heros, and as I am also a pilot it brings me into contact with fellow aviators.
However, as time has gone on men are larger than back in the 1940s, so many prefer the 55mm size sunglasses. Those with round faces sometimes prefer the 58mm size aviators.
The most common Randolph Aviator size and combination are the 55mm size with Neutral Gray lenses and Matte Chrome frames. For most the 23K Gold frame is too bright, and they find them distracting.
The same holds true for the AO Original Pilot sunglasses as well, but the preferred frame finish is the 23K Gold EP (Electro Plated) finish.
We love to hear from fellow pilots, so if you have any questions send us an email or give us a call - we always welcome those conversations.