I like to think that apart from useful artefacts, Charles keeps various objects that appeared in the living world after he passed away in his backpack.
I believe he is very proud of his collection, i mean he's got gadgets and gizmos aplenty, he' got whozits and whatzits galore.
Edwin is unimpressed by things that are useless for their work and sometimes make it harder to find required items and does not understand why Charles fondly calls him Sebastian when he scolds him for this mess.