Dear Jack:

I have a U-293, baby-blue glaze, and with an underglaze G-P marking (cobalt blue ink). You don't show this marking in the second edition of your Porcelain Insulators Guide Book. Any ideas an who made this insulator?                                                        

Are the "G" marked insulators found in any styles other than U-11A, U-50, U-229 and U-236?

At the 1981 NIA National in Sacramento I picked up a sleeve stand with incuse F. M. Locke marking an the base. It has a light brown glaze with slight greenish spots. I have seen these with U-377 to U-380 helmets in the eastern part of our state, and I matched mine up with a U-379 with similar glaze for my collection.

I am. curious about whether this matching in unusual? I asked a few porcelain collectors at the National about it, and they said, "No, they were used with the larger multipart pin types." What's correct? 
Brent Burger, NIA #2657 
Bellevue, Wash. 

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Dear Brent:

On your U-293, the Monogram-CP marking is the registered trademark of Canadian Porcelain Co. In addition to this marking, they also used several forms of "C.P." markings on pin types. My book concerns only U.S. insulators, so natch that marking isn't included in the book. 

Regarding your "G" insulators, these are known in styles U-11A, U-50, Sim U-55, U-229, U-236, Sim U-250, and U-272. 

What you call a "sleeve stand" is in reality the porcelain portion of a "porcelain base pin assembly". These were a Fred Locke creation (patent March 14, 1893), and the idea was that the porcelain base would cure the problem of wooden pins being charred by lightning flashover, just as it is cured by modern steel pins with only a wooden cob. These pins were cataloged and sold an a complete assembly -- the long pin bolt, the wooden cob at top, porcelain base part, washers and securing nut.

A complete line of these porcelain-base pins was made, stocked and cataloged, just an with other lines of or steel pins. There were all types and sizes -- something that would fit any type of insulator you wanted to use, those made by Locke or any other company. The various sizes could have been (and were) used with a multitude of insulator styles, especially styles lacking long extended interior petticoats. Their use with helmet style insulators wouldn't have been unusual. 

Porcelain-base pins were made by Locke for a number of years, and also by other companies (most notable Illinois Electric Porcelain) after the patent expired in 1910. Their use came to a rather abrupt halt when it became general practice to use all-steel pins for power insulators. These were much cheaper and more reliable than wooden pins or the porcelain-base pin assemblies.

Porcelain-base pins are not rare, but might be classed as uncommon. Early ones with Fred Locke markings are fairly good items, but I would think the value would be best for a complete pin assembly, not just the porcelain base portion of it.

Jack