I bought the one on the right from Calgary collector, Ted Ingram years ago. I always thought it was English, like the two beside it are. Since then I have never noticed another like it. On the left is a U-1392 similar in size. 4 x 2.5 inch.

Caleb Thimell writes,

I have never seen this style porcelain insulator before and it is not documented in any of my books. I agree there is some resemblance to the other British porcelain insulators next to it. Actually, I believe this is a piece made in Ireland by Belleek Pottery. Based on the porcelain color, transluscent glaze and similarity to the one next to it which I have identified examples as originating from Ireland and made by Belleek. Porcelain articles are known to have been exported to Canada so its possible insulators too, although I would expect to find it marked. However, the original owner could have obtained it from a contact in Ireland. If so, a piece made for the domestic market would not require a mark. Typically, they are found with the PTT mark on the skirt stamped in black ink.

In the absence of other markings (look very closely on the dome, skirt, base and inner skirt as often a date or other identifying mark can be found), I believe Belleek made your insulator.

Caleb Thimell