Bob G : First, I am guessing that you meant "provenance:, not "providence", right ? And no, I don't think that in this day and age, the Posting of an image, especially, and suspiciously, without accompanying text of any sort, can be provenance of the statement. Anyone with even a rudimentary knowledge (like me) of Microsoft Paint, or Photoshop can come up with all kinds of things (see attached).
However, unlike Jim, I do not think it has anything to do with "Police", mainly because police items are covered under the "Model Identification Codes" and "Abbreviations" by either "P.I" (Police Interceptor), or by "P/C" (Police Car).
I do think something similar to the original image Posted (General Parts Division), is probably correct, and even it may be correct, but without documentation, who knows.
I do know that in the Ford Warranty Manuals of the mid-sixties, they refer frequently to the "Parts Depot", and it seems to make more sense in the context in which "GPD" is used.
Still hoping for some documentation.
Bob