Collectibles--General (Modern)/Thomas Insulators


3 Thomas Insulator photos.jpg
3 Thomas Insulator pho  
Hi Bob, and thank you for your help & expertise...

I purchased 3 Thomas insulators at a recent estate sale, and was wondering if you could tell me a little more about them (i.e. where they were made, possible age, and perhaps what they might be worth).  There are some small chips on two of them, and a few white spots that appear to be in the glazed finish.  They are also a strange mixture of colors... appearing dark blue in some places, to dark or light brown in others.  I have attached some photos, if that helps too.

Thanks Bob!

Hi Bill,

We call the style of insulators you found a signal insulator.  These were frequently used on the power lines to drive railway signals and other lower voltage applications.  These were also extensively used for rural power delivery.  I would date your items from the late 1920s into the early 1930s.  R. Thomas & Sons was based out of East Liverpool, OH and made insulators from the late 1890s through the late 1950s.  These are collectible, but pretty common, with about a $1.00 value each.  Still these are great pieces of history!

         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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