What Does The "Bosg" Or "Bdsg" In The Center Of This Cancel Stand For?

It's on a military parcel tag, so is it a U.S. military designation? Is it a location abbreviation? Google comes up empty...

Thanks.

Base Operations Support Group comes to mind.

BriDeSburG a station in Philadelphia adjacent to which the Frankford Armory was located.

Your tag is a Zone 1, 30 pound parcel post (5 cents first pound, 1 cent each additional pound for the next 29) item with properly assessed 2 cents of WWI parcel tax (1 cent/each at least 25 cents or fraction of postage, not fees) mailed from between 11/2/1917 and 12/31/1921 inclusive, the period for which the parcel tax was assessed.

The documentary was to be manuscript cancelled by the sender, but that was not always followed.

Thanks guys. Appreciated.