Here is the information I have about this piece. It was found at the bottom of the bank of the Philadelphia Freight line tracks. It was "freed" during a period of heavy rain/snow flood in 1999. Two were originally found. The person who found them, to this day, can not find the second one!! I do not know any more about the specifics of the exact location. But, it was along a RR.
As Brett pointed out you can see how the groove on the "spout" lines up with the groove on the body of the insulator. If a "tie wire" was tied between these, its only purpose would be to prevent the line wire lifting up from the slot and coming out of it's slot. This arrangement would keep the wire in place, allowing it to sag freely between insulators.