G.W. Carter got a patent for his "Two Color System" March 3, 1908.

He said red insulators would be used for dangerous voltages and normal colors for all else. He also mentions each should have its own embossing - hence "Oregon No 1" and "Oregon No.2" embossings shown

On the left is Insulator A, in red, with a groove on top (not showing well in the picture - but it is in the description as being there) to hold the vertical tie wire.

On the right is a normal colored insulator, C, with a transverse hole above the pinhole for the wire to pass through.

Both pins have a transverse hole for the vertical tie wire to pass through.

It would be fun to find them, but I can think of a number of possible reasons why these were never used, and I was never a lineman: random dome glass thickness, stress over the pinhole and concentrated on two points on the skirt, inner skirt could cover the through-hole in the peg, red glass color expensive, using two tie wires is more costly, holed pins making for faster deterioration and breaking due to tension, etc.