Dear Elton,

I recently purchased an insulator that I thought you may find of interest. My fat friend was found at a flea market and I cannot find a U-number for it (See photo below). An insulated wire is imbedded in the groove between tie petticoat and the skirt and has been checked for continuity.

It is 4-1/2 inches wide and 4 inches tall and looks fat. It has an incuse marking consisting of an insulator insignia with LOCKE R=oo inside.
Jeanne Bridges, NIA #1027

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Dear Jeanne,

Your "fat friend" is a real goody, and is about the best find of the past couple of years. Your thought that I may find it of interest is a pretty big understatement! It would be nice to place it next to it's compatriots U-173 and U-174, but there have been so many precedents of putting like shapes in groupings that we're stuck with making this new thing U-275 (where its' in with like shapes).

The U-275 is a dry-spot insulator, the exact same thing as the U-173 and U-174 that were made by Pinco in the late 1920's. In these, the insulator in designed with a very deep groove between the skirt and interior petticoat. An insulated wire is placed around the depths of this groove halfway around with each end being bent down out of the groove on opposite sides. Then the groove is filled with a tar or other potting compound. Needless to say, this arrangement affords the necessary dry spot on the insulation of the embedded wire -- thus breaking the leakage path along the wet insulation of the bridle pair connected to the open wire line.

The dry-spot was used on a telephone circuit where a tap into the line was desired. To prevent the circuit from becoming unbalanced during wet weather, resulting in crosstalk, the insulated tap wire is provided a dry section, by the dry-spot insulator, of several inches to break the leakage path. Naturally, a pair of this type insulator would be needed for each phone tap, one for each of the two leads. A more practical and serviceable dry-spot is the U-I 88 which is specially designed to make dry spot provisions for both phone tap lead wires within in the insulator. The more practical U-188 was manufactured for about 30 years.

The dry-spot insulators were made with a tie-wire groove. One of the normal conductor insulators was removed and replaced by the dry-spot which then accommodated the conductor wire and provided the tap wire and dry spot. As an alternative, the dry-spot was mounted on the peg of a transposition bracket underneath the crossarm. Further detailed discussion of dry-spots can be found on pages 121 and 153 of Jack Tod's book Porcelain Insulators - Guide Book for Collectors, 2nd edition and CJ article 9-73-18.

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The U-275 is of great interest because of the 2-26-1929 patent on this scheme by Postal Telegraph Cable Co. -- the Insulators (styles U-173 and U-174) being made by Pinco. The Locke marking on your "fat friend" was used from 1922 to 1928. The year that your item was made by Locke is very important, since it could have been considerably prior to the 4-29-1927 filing of the patent (see Jack Tod's new book, Insulator Patents, 1880-1960, Tod class 52). Naturally, things are not patentable If they have already been invented and made by someone else at a prior time, whether or not the originators filed for a patent. A patentable item must be novel and also an original invention, not a copy of someone else's prior scheme. A drawing of the dry-spot style was made by Pinco dated 9-30-1925 (shown on the preceding page) . Pinco was evidently manufacturing the dry-spot, it only experimentally, as early as late 1925. Possibly the nearby Locke plant at Victor out-bid Pinco on an order in the 1927-1928 time period before the Victor plant was closed in 1928 and subsequent discontinuation of the Locke R=oo marking. The U-174 version carries both the Pinco marking and the underglaze ink marking shown below.

Elton

In February 1985 CJ page 23, we ran a list of known Pittsburg date control and full date markings and a request for your reports of markings not shown on that list. We must have had a near complete list as only two people responded with new reports.

A. L. Rash reported the unusual JAN-9 919 marking. The marking was deep and clear but there was no indication of the "1" in the year "1919". This year is very late in Pittsburg's history.

Frank Phelps caught all of us asleep with three new reports: APR 30, MAY 2 and May 6 all from 1913.

Also note the typo error which should read "AUG 12 Rec'd" instead of the month "APR". The updated list appears on the following page and we welcome any new additions. New reports will be published individually.