Ryan B, first let me welcome you to the forum.
What I can see from the pics (these are sharp but small and therefore lacking some details - can you please show pics of the middle scabbard fiiting and a pic of one of the death head segments?) it looks to me like a nice, early (all nickle silver) socalled Mod.II chain (from TTW).
These early (if it really is an early one) nickle silver chain links were delicate and tended to open their welding seams and to bend. So most propably this link was easily lost during wear.
Nevertheless the dagger is in overall very nice condition and the 400$ for sure pure luck.
As the wearing of portepees were only allowed to Waffen SS members late in the war, I personally would tend to let such an early dagger, worn by an Allgemeine SS member in early 30ies times, without portepee. Naturally the wearer could have changed to Waffen-SS and could have worn this dagger later in the war too but the character of these early chained daggers would be (for me) without portepee.
I more would tend to look for one of the rare hangers.
Just my thoughts.
Regards,