Glass Insulator Embossings

Embossings (Markings) Found on Glass Insulators
(and their possible glass factory sources)

Below is a brief list of some embossed markings seen on insulators that stand for end user companies (or in some instances, a brand name or initials used by the glass company) which may not obviously indicate the factory that made the piece.  It would be difficult to extrapolate on subtle, minor embossing details that, in some cases, might distinguish similar-looking insulators as being products of a certain glasshouse.   As an advisory, I should mention that the information presented below is not guaranteed to be 100% accurate. It’s to the best of my present knowledge, and I would appreciate any corrections or clarifications submitted, so please feel free to contact me if you can help out!   I would also recommend consulting various reference books within the insulator collecting hobby, as well as other knowledgeable collectors, for more information on the subtle differences between the products of different glasshouses.  A very good source of info would be back issues of Crown Jewels of the Wire, the magazine of electrical insulator collecting which has been published each month since 1969. Many informative articles have been published through that venue.

NOTE: For more information on the individual glass company/factory names mentioned below, please check out my webpage on GLASS INSULATOR MANUFACTURERS. Thank you!!


 PRIMARY EMBOSSING………………………GLASS FACTORY SOURCE

A. T. & T. …………………………………….Brookfield Glass Company
AM TEL & TEL…Brookfield, Hemingray, Western Glass Mnfg.Co, Sterling
B (on the side, normally below wire groove)……….Brookfield
B.& O. …………………………………………Brookfield, Hemingray
B. G. M. CO……………………………………………………Baltimore
Birmingham………………………………………probably Lynchburg
Brooke’s……………….Uncertain New England-area glasshouse
B.T.C…………………………………………………………..Diamond?
C.& P.CO……………………………………………………..Brookfield
C.D.& P.Co…………………………………………………..Brookfield
C.E.L.CO………………………………………………………Unknown
C.E.W…………………………..San Francisco or Pacific Glass Works
C.N.R…………………………Unidentified Canadian glass company(s)
C.P.R…………………………Unidentified Canadian glass company(s)
Cable…………………………………..Brookfield, Hemingray, others
City Fire Alarm…………………………………………..Brookfield
Columbia……………………………………..Hemingray, Brookfield
Combination Safety……………………………………….Brookfield
Diamond logo……………………………………..Diamond, Dominion
Diamond superimposed over oval and I…………Owens-Illinois
E. L. CO…………………………………..Brookfield or unidentified
E.R……………………………………….at least some are Brookfield
E. R. W………………………………………………………..Unknown
Fall River………………………………………………….. Brookfield
G.E.Co……………………………………….. Brookfield, Hemingray
G.N.R………………………………………………………… Diamond?
G.N.W……………………………………………………….. Diamond?
G. T. P. TEL. CO………………………………………Canadian company
H (on dome, beehive style insulator)………………………….Hemingray
H.G.CO………………………………………………………Hemingray
H.G.W.(monogram)…………….probably Houston Glass Works
I (thin raised vertical line, on opposite sides of the skirt of beehive style insulator, with “H” on top)……………Hemingray Glass Company
Jumbo……………………………………………………….Brookfield
K. C. G.W. ………………………………………King City Glass Works
Kimble…………………………………….Hemingray (Owens-Illinois)
Knowles………………………………………………………….Novelty
KPP inside an oval………………Kerr (Kerr Packaging Products Division)
£ (British “Pound” Sign)…………………………………….Sterling
L.G.T.&Co……………………………………………………Brookfield?
Locke………………………………………… Brookfield, Hemingray?
Lowex………………………………………………………. Hemingray
M.& E.Co………………………………………………………Unknown
McMicking……………………………..Uncertain Canadian company
Montreal……………………………………………………….Diamond?
Mulford & Biddle………………………………………………Unknown
N.E.G.M.CO……………………..New England Glass Mnfg. Company
N.W.& B.I.T.Co……………………….Unknown Canadian company
N.Y.& E.R.R…………………………………………………….Unknown
P in a diamond (CD 134)……………………………………….Unknown
P in a diamond (CD 154)………….Canadian manufacture, probably Dominion
P.R.R…………………………………………………………Brookfield
Paisley…………………………………………………………Unknown
Patent Dec.19 1871………………………………………..Hemingray
Patent Oct. 8 1907…………………………………………Hemingray
Patent Oct.8TH 1907 [NOTE “TH”]………………….Brookfield
Patent May 2 1893………………………………………..Hemingray
Pettingell Andrews…………………………………………Unknown
Postal…………………….most are either Brookfield or California
Pyrex……………………………………………………………Corning
Prism……………………………………………………………Novelty?
Santa Ana……………………………………….California, Hemingray
Seilers…………………………………………………………Hemingray?
S.F……………………………………………………………….Uncertain
So.Mass.Tel.Co……………………………………………..Brookfield?
“Star”…..Novelty, Sterling, Harloe, probably some made by Brookfield
Sterling………………………………………………………….Sterling
Surge…………………………………………………………..Hemingray
T.H.E.CO………………………………………..Brookfield, Hemingray
T.C.R……………………………………Unidentified Canadian company
Tillotson…………………….Brookfield ; New Windsor Glass Works
Twiggs……………………………………………………………Unknown
U.S.TEL.CO (CD 121)………………………………………..Brookfield
Westinghouse…………………………………………………..Unknown
W.E.MFG.CO……………………………………Brookfield, Hemingray
W.F.G.CO………………………………….Western Flint Glass Company
W.G.M.CO………………………………..Western Glass Mnfg. Company
W.U………………………………………………… Brookfield, Hemingray

 

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Comments/Replies: All comments are moderated so will not be published immediately. Because of mail volume received, and time and energy restraints, some questions may not be answered individually, especially if the subject is already addressed elsewhere on this site. This website is not intended as an appraisal service, but as a resource for background info on glass companies and the marks they used, so I usually delete "What is this bottle worth?" types of queries. Thank you very much for your patience & understanding !!