not a spacer or shim, just a bit of oiled paper to help avoid parts seizing together, not necessary, but you could replace it with a piece of butcher paper or brown paper bag if you're shooting for 'original'
"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir "When we tug a single thing on an old truck, we find it falls off" ~ me Some TF series details & TF heater pics