This is a plastic protractor I turned up some time ago. I can't find any information on the S M Co., although a company using these initials (the Southeastern Metals Co.) did make canteens for the U.S. Army during WWII. It looks like it might have been used for plotting coordinates for military ordnance.
I believe that company is Sillcock-Miller. They made the same type of protractor for the military in the '50s and '60s, too.
ReplyDeleteMuch thanks!
ReplyDeletehttps://airandspace.si.edu/collection-objects/plotter-navigation-navy-sillcocks-miller-corp/nasm_A19700388000