Here's a different one. It is a CD 115 EIN [040] (F-Skirt) Armstrong's No 3 (R-Skirt) MADE IN U.S.A. [A in a circle] 20-51.. SB in off clear with a flake off the dome edge. It has a different type of tie mechanism to fix the line wire to the insulator. I'm guessing it's made of an aluminum alloy. The surface facing the insulator is engraved "Reliable" in script in one corner, and CAT NO. 5058 is stamped across the bottom. I've not seen one before, have you?

UPDATE: Apparently, this is not a tie wire, according to Donald Woods. It's a 109HSS dead end. Thanks, Don.

Now you can add it to your go-with collection for just $8 plus postage.