Best guess is that LLH supplied the barrels and got them from Krupp. I suspect it was a special order or maybe LLH was the jobber/agent for the barrel blanks.
Lefever seems to have been willing to make or supply almost anything to make the buyer happy. He certainly stocked and engraved his guns as well as any other maker. No Henry Ford any shade of Black attitude here. Makes Lefevers a real interesting treat to look at some times as you never know what you may see. I have a G grade with one of the fanciest stocks that I have and it would be happy on one of his very highest grades. And the G grade was the most common, lowest grade for years until the H, I and DS were brought out. The stock blank would cost more today than the gun. Burl figure with very nice color.