This is a blue glass insulator. The insulator looks like the only in the 1984.10 accession, but did not have a number associated with it. The insulator measures 4.25" (h) x 4" (dia).
Lexicon
Nomenclature 4.0
Nomenclature Primary Object Term
Insulator
Nomenclature Sub-Class
Electrical System Components
Nomenclature Class
Electrical & Magnetic T&E
Nomenclature Category
Category 05: Tools & Equipment for Science & Technology