Again, we have the case of various cases, made by one company, and loaded with another’s Powder. This situation still occurs today…a lot of European Brands of Shotshells have their shells made/assembled by one of the Major manufacturers, then loaded in house by the Customer with somebody else’s Powder, and sold under a “trade brand”…so that the headstamp (usually a Generic type, such as “12ga and ***” is the Headstamp Id (NO factory indicator) and the body label refers to whoever “filled” the case, or even to the Retailer/wholesaler who ordered the Lot.
BTW, “Diamond Powder” is not just a trade name, but is a descriptive name for Diamond-shaped Flake Powder ( actually little Rhomboids of flat Nitrocellulose or N/C and NG Double base…Extruded as a flat sheet, then sliced by rotating disc knives into strips like Tagliatelle Pasta, then cross cut (or guillotined) at an angle of the strips to create a "Diamond "Shape. Frrench and German Powders of before WW I were made in this fashion; eventually German Powders settled on a “Rectangular /Square” shape ( final slicing was simpler) such as G.Bl.P ( Gewehr Blattchen Pulver…Rifle Flake Powder)
in use till the end of WW II.
Current European Powders with “Diamond” shapes include the RIO series (Now Maxam of Spain, formerly UEE)…all their shotgun Powders are Rhomboid flakes. Italian Powders can be both Square and Rhomboid, as used by Fiocchi ( Powders such as Baschieri & Pellagri, and SNIA Viscosa.)
IN Turn of the century ( early 1900s) Ammunition, identifying the Powder used was a marketing Tool, given the good market response C&H already had with its Black Powder… It’s like saying, if it’s by C&H, thenit must be good!"
Once the initial patents or registrations ran out, anybody could make a similar Powder (Flake Diamonds) ,but could not call it “Diamond” as this was a TM registered by C&H…of course, Eley would have had a TM Licence agreement with C&H for the use of the TM on their cartridges. ( so many pence ( or fraction there-of)per cartridge produced)?