Searched along an older line and found this unusual OB copper-top multi I have not seen before. Anyone know the M# for this one? It looks as if the copper crown is too small for the top shell.

UPDATE: This is an Ohio Brass "Red-Top" RFI treated insulator. The recessed groove around the base of the crown is intentional and was designed to allow for full-crown metal coating as well as corona control. Thanks David!