This multipart insulator according to several reviews from ICON is the closest to M-2315 with the Victor Locke logo with the PATD abbreviation visible and a faint visible date underneath which is rare compared to the "standard" Locke logo. It was found here in Norway and from what I could find they were used in the construction of high voltage lines connecting hydroelectric power plants and paper mills and others in the 20s-30s. That's pretty much all I know, the insulator itself is without damage or cracks has a "glued" thread reduction as seen in the pictures, see pics 1,2 and 3. It weighs a little over 3kg, it can be yours for $80 including shipping from Norway, PayPal FF preferred.