Lee:

        Here are some of the ones I find most useful.  I have marked
        the
best for glass insulator identification with an asterisk, but all of
them contain useful dating and historical information.  Gish and Tod
are aslo very helpful with porcelain insulators.

Gish, Elton
 1988 Multipart Porcelain Insulators.  Infinity Press, Buna, Texas.

*McDougald, John & Carol
 1990 A History and Guide to North American Glass Pintype Insulators.
Volumes 1 & 2.  The McDougalds, St. Charles, Ill.

Milholland, Marion & Evelyn
 1976 Most About Glass Insulators: Milholland's Final and Complete
 Glass
Insulator Reference Book.  4th Edition.  Marion C. Milholland, Tacoma.
Wash.

Tod, Jack H.
 1988 Porcelain Insulators:  Guide Book for Collectors (Unipart Pin
 Types).
Infinity Press, Buna, Texas.

Woodward, N. R.
 1967 Glass Insulator in America:  1967 Report.  Press of Premier,
 Houston.

*       1988 Glass Insulator in America:  1988 Report.  Privately Printed.

Hope this helps,

Bill

----------------
Bill Lockhart
New Mexico State University
Alamogordo, NM
(505) 439-3732