Doing a search on “HP115” produced about the most eclectic bunch of stuff I have ever got from a search engine.
Concrete Products, Handley Page 115 (what we are really interested in), Picture No hp115 from a porn site (not even good porn) even Hush Puppies have a shoe of that nomenclature. How about Hand Painted Sarongs and something called “FUZOKU/KYOSHOU” –whatever that is.