Vintage photos of:
1912. "Post Office Department. Hupp Auto Railway Service" (i.e., Hupp Automatic Mail Exchange, a system for transferring mail bags to and from a moving train). Harris & Ewing Collection glass negative. Note the two utility poles at left that have been scratched off the negative. View full size.
An uncaptioned circa 1915 photo showing the assembly of what look like locks or latches inscribed "U.S. MAIL." Like any progressive workplace, it's equipped with spittoons. Harris & Ewing Collection glass negative. View full size. Update: These are "L.A. locks" being assembled at the Post Office Department's Mail Equipment Shops, 2135 Fifth Street N.E. See the comments for details.