Here's an uncommon porcelain t-bar insulator found in Colombia with incuse mark "4579." Most t-bars are unmarked. Measures 2"w x 3 1/8" tall. Light use marks and tiny base nick that created 1/2" hairline (so small I didn't see it initially. Price dropped accordingly). Also some very light rub marks in the saddle groove.

Maker unknown, but I believe I've seen this in a German catalog (Hermsdorf or Rosenthal). It came in at least three sizes. The large size was also found in Colombia and it was marked but I've only seen two examples. This size I found about half dozen. But they rarely come up for sale!

First email gets it for the reduced price of only $37 plus $8 postage. Thanks!