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Collectibles--General (Modern)/JD blue glaze porcelain insulator


Hi Bob - I have a large electric insulator - that is blue glaze porcelain (approx 10 1/4" wide x 6 3/4" tall - at the most wide & tall points of measure), and has an ink stamp under the glaze that has the initials JD in a circle above the date MFG. AUG. 1936. Could you please tell me your estimation of how much value it could have? Thank you!

Sorry for the delay in this answer, I was out of town.  What you have is a Jeffery Dewitt power insulator.  These were made from the mid 1920's up to WW2 in the early 1940s.  Jeffery Dewitt or JD used a beautiful blue glaze on many of their insulators.  From your dimensions yours is one of the more common styles, but they are still tough pieces and very collectible.  In good condition these usually trade in the $25-$35 range.  These are rated for about 35,000 volts.   Hope this helps --

         Thanks, --Bob

Collectibles--General (Modern)

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Bob Berry


Questions related to collecting Glass Insulators and porcelain insulators - I can provide historical information as well as current collector values. I am also interested in purchasing insulators I need for my collection.


I have collected since the early 1970's and have much historical information, as well as knowledge of current insulator values.

National Insulator Association (

BS & MS in Electrical Engineering

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