Early A-C Spark Plugs

 by Rich Street
Member: Spark Plug Collectors of America & Society of Automotive Historians

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c. R. Street 2005

c. Rich Street 2005

1912 Style

Photo by Wayne McPherson

Note bullet shaped top nuts on 1 and 3, Buick.
Note differences in base threads between 2 and others, it contained flat bottomed insulator pictured below.

Un-numbered.
Note Brass Hold-Down Bushing on #5 and very slight taper of Porcelain.

Photo by J. Moore 

Note very slight logo differences. No trademark record of this logo is found on record.

 

AC and Ford:


Photo by J. Moore

The "Ford Special" as well as other AC, Champion and Mosler plugs was stamped with a patent date of October 18, 1898. I believe I have narrowed it to 612,614; 612,615; 612,701; 612,779; 612,783; 612,801; or 612,802.

 

Any information or clarification would be appreciated.

 

Note "dot" under the 2 and end differences

Photos by R. Street