Washer

This is a plain washer that shows up once in the parts books, filed under motor unit fitting and footrests. Not much more to go on here beyond that it's a washer used somewhere in that mounting hardware. The manufacturer listed on file is Lucas, but Lucas made electrical gear, not washers, so that tag doesn't hold up against what the part actually is - just treat it as a generic hardware washer tied to the motor mount/footrest area.