Here is a Kamikaze pilot posing with what is likely a family heirloom Katana.
Notice the typical mounting.
Of course not all Japanese soldiers and pilots were descended from Samurai, (most weren't) so naturally they had no family heirloom Katana.
So for those the typical western style mountings.
I've seen evidence online, of those western style fittings changed over to traditional fittings.
My Iaido sensei uses one I believe.