In this case it is the 1940s. A couple of weeks back I was working on two complete (sash and frame) windows from a CCC log restroom for the Emigrant Springs Heritage Area. The restroom has been converted into a storage unit for the park.
During the restoration process I discovered some signatures on one of the bottom rails. After some discussions with the state historic preservation office we decided that it would be best not to paint over it. A clear coat was put over it instead.
I never think that all those scratches and scribbles you see in public restrooms could someday be considered historic.