This rather unique insulator uses the top skirt mold set fo an early M-3725 glazewelded to an M-2998 collar skirt creating a unique rare varient of the very scarce Fred Locke M-2998 . Less then five frepaired examples of this insulator exist. All have marking 6-1. As far as we know they were all origionally installed on the Colgate line in 1902... and remained in service only a very few years . They were later reused on other lines at lower voltages. Compair this to the more well known M-2998 Fred Locke which has a smaller crown and smaller collar [id=308697615] . I believe these were produced slightlty later then the other version. The other more common version seems to have a very thin crown and may have been prone to punctures do to the thin ceramic of the crown these are definitely thicker and beefier. I suspect that as soon as the M-3725 became popular as a proven design the M-2998 became obslolete instantainiously. the first production of the M-2998 was likely in febuary or march of 1902 judging by glaze color characteristics units like the picture above were most likely produced towards the end of 1902 or early 1903. Photo by Paul Greaves.