See write-up of this pair of insulators on the ICON mailing list. The insulator on the left is an unembossed CD 370 from Australia. The insulator on the right is a CD 370.x from Canada. The one on the left has a copper cap, the one on the right has an aluminum cap. A CD 123 and CD 154 have been added for size comparison purposes.
[IFONA CD ???]