Here is the reverse side with the single line patent date, as compared to another with the usual PATENTED // APRIL 12 1910

Smaller lettering on the single line date, compared to larger lettering on the other embossing style

The question still remains, why the upsidedown PAT. APPLD FOR on the front skirt, with the granted patent date shown on the rear skirt.

Is it possible these units were made in 2 piece moulds, and perhaps someone used an "outdated " mould half? That's my best guess.