Collectibles--General (Modern)/glass insulator


I have a glass insulator. It says Armstrong's DP1 and Made in U.S.A., then @ or an R in a circle, then 20 52:..

Is this worth anything?

Hi --

You have a telephone style made by the Armstrong Cork Company in Millville, NJ.  This is relatively recent production with a manufacturing date of 1956 (52:.. tells me that the mold was made in 1952 and used for four years before making this insulator).  Insulator collectors have come up with a numbering system for the various styles called the CD system.  Your insulator is a CD 155.  These are pretty common in clear glass with about a $1.00 value or so.  Still a nice piece of history that is nearly 60 years old.

         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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