This is the only all white historic early multipart known to have been used in North America. The "Shawinigan Insulator " named for the Shawinigan Waterpower Co Quebec used these on there first long distance power line to Montreal, QC . Historicly, all insulators of this design were known as "shawinigans". The line and insulator were designed by Ralph Mershon in 1902 and operated @45kV .
The earliest production of these insulators had very thin fragile skirts with a squared off drip edge as this specimen has . A second line was built a year or two later that again used these same insulators with much thicker beefed up skirts. this insulator is one of the early thin ones and was kitsulatored together from repaired lower skirts found on the line and an unused top found on eBay . The top could have been found in the Thomas dump but is clearly identical to those found on the Canada line . These insulators were only in service till the late 1910's when they were replaced with large Goddard type multiparts.
A few brown glazed specimens of this same type have been found used in Westinghouse made switchgear in power plants and substations in New York, Idaho and western Washington state. Fewer then twelve brown ones have survived . This white one, found by myself and Paul Greaves in Canada, and an undisclosed number of other white ones were found by Ken Willick and Jeff Katchco in New York purportedly on the sight of the Mershon experimental test line . Both the brown and white M-3250's remain very rare. All of the known white specimens were damaged and repaired . The Shawinigan line was very well cleaned up and for the most part no evidence of the historic line can be found other then pole holes in rocks in a few of the more more rugged places. Very sad for us collectors! :-(