Here's the double-threaded 143 I showed photos of being found [id=452636565;here]. I had to soak it, clean the dirt and grime off, and re-glue the piece that had separated from the base. Fortunately the crack was extremely clean, so the repair looks good.

This is probably only the fourth double-threaded CD 143 I've ever personally dug. It's the [030] embossing style and bears the same mould imperfections as some of the CD 743.3 examples in the hobby, indicating it was made in the same mould.

These double-threaded 143s were possibly produced as a means of installing a sharp-threaded insulator onto a threadless peg just after threadless had begun to become obsolete. Linemen probably preferred these over the threadless as they would thread snugly onto a threadless peg. I've personally tested it!

These probably date to the mid 1870s or so and are contemporaneous with the end of threadless insulators in Canada.