That's a nice looking dirk. There is a long history of accessories being stored in the scabbard. I don't know if the information I have is entirely dirk related. The Swiss and Germans both used to do this on their short sword scabbards and with their hunting trousses (A large knife with other smaller knives used to dispatch wounded animals and dress the kill). That's based on the findings from the mid 1400s and 1500s. Many people in the middle ages used to carry a small pick or bodkin in the same sheath as their knife, and there have been some Japanese swords found with knife and pick in the scabbard. In renaissance Italy the knife on the short sword had a specific name, but I will have to edit it in when I can get to my reference material. It seems to be a fairly common thing to piggyback the accessories, at least historically. I'm sure there are others on here with more dirk specific knowledge, but I thought this was at least loosely relevant.