I remain open minded about these little knives, and it is certainly an enigma, to be sure.
Say you already have a stock of the little knives without the HJ diamond on the scabbards. And you want to mount an HJ insignia for some special up coming event. You're only option would be to mount the diamond or whatever insignia on the scabbard, unless you have a stock of spare grip plates with the diamond recesses molded into them standing by. Not likely. Because I am completely convinced by the testimonies of people like Ron Weinand, Tom Johnson and many more, and I know where this one came from, I know these were produced during the TR period. Or shortly thereafter, but not in the 60s or 80s. Can I prove that with an affidavit? Sadly, I cannot. You can tell, while holding it in hand and under close inspection, that the mounting of this insignia was not haphazardly done. The above is only my opinion and theory .. Makes sense to me ..