My recent find. Early M1910 aluminum canteen and cover.

I recently came by this canteen w/cover in the bottom of an auction box of unrelated miscellaneous stuff.
The cover is clearly stamped FMESCo Oct 1918 on the inside of one of the flaps. I have found numerous references to 5 companies that manufactured canteens and covers during this period, but am unable to find any reference to FMESCo. The canteen itself has no stamping or makers marks. It is a welded seam model and with no mfg markings on the canteen I think that dates it to btwn 1912 (start of the welded seam) and 1918 when they began stamping the canteen wit mfg. and year. Plus the cover is marked oct. 1918. My biggest mystery is the nickel size affixed to the cover and clearly marked U S over a banner marked HQ56.23 over crossed infantry rifles. I have been unable to find ANY photos or reference to a brass button affixed to the cover. Any ideas?