Do you think the Leather Washer is not from the period?
I think nobody in the world can tell you when the leather washer has been replaced. Might have been done during the period, perhaps later.
But it seems not to be the leather washer with what the dagger has been produced by HÖRSTER.
On the other side, I would not put too much weight concerning the leather washer. It has only been a remark from my side, obligated to truth. You do own a VERY nice and scarce group! One of the nicest sets I have seen. I do know several collectors who do look for such a good conditioned set for years but cannot find any.
And -honestly- these daggers were also worn with belt loops you do show. The "special" belt loops are rarely encountered.
Regards,
