This is one of (at least) three different molds of the [250] stamped-embossed HEMINGRAY NO 9 / PATENT MAY 2 1893 insulators in which a "V" stamp, oriented upside down, was used (hammered into the mold) instead of an "A" stamp. This is probably not an "error" in the true sense of the word, as it appears to have been intentionally done by the mold engraver. Update... here's another, different individual insulator, but produced from the same mold: [id=325174484] .