Just noticed this interesting post. I like all of the parts, when they came together we may never know. Ivory grip on a depot piece of course does not fit as has been noted. Perhaps a hint to the age is the thick leather washer. Imperial ivory grips are shorter than Third Reich Navy grips. I looks like this washer was used to make up the difference.

In our German book on navy daggers we have one of the original receipts for a depot dagger. Who signed it out, when and when it has to be returned. The agreement also states if the dagger is not returned on time the borrower has to appear before a judge.