Dear Jack: 

I have been intending to drop you a line since your request for Pittsburg "date control" markings first appeared in your column last July. 

I picked up two mahogany brown Pittsburg U-933 glazewelds in Maine last summer. One is unmarked, but the other one has a date stamp "JUL 8 PAID" just below the unglazed top firing rest.

Also, Jack, you might let me know what the approximate value of these might be.
Len McGowan 
Webster, N.Y. 

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Dear Len: 

Many thanks for the report of this date stamp. It seems like a long road, but hopefully someday we'll get enough of these "date control" markings reported by collectors to crack Pittsburg's dating code by the method suggested last year by Matt Grayson. 

On these old insulators, it's not so much a problem in determining exact "value" as with locating someone who wants or needs the item for his collection. I've found that it doesn't help to put a $1 sticker on a $5 insulator at a show if no one happens by who wants the item, but the insulator would quickly sell even at a premium over the $5 to anyone who really wants it for his collection. If forced to punt on these specimens, I'd put a sticker of $4 to $5 on the unmarked one and maybe double that on the dated one. These aren't old classics, but nevertheless are nice glazewelds. 

Jack

Dear Jack: 

Last week I picked up an interesting item at an Arts and Craft show in Anaheim. It is a white Imperial similar U-927 (but 5-1/8" x 3-11/16" and with innermost petticoat recessed upward about 3/16"). 

I have two of the larger Imperials such as this shape but never knew these smaller versions existed. There is a small defect above the trade mark where the glaze didn't cover a rough spot, but it is in good condition otherwise. 

It has three markings -- the crown trade mark, the wordy "Manufactured by..." stamp, and a date 6-17-01. This trade mark isn't quite like the one shown in your book, since it has some extra elements above the band that look like the clubs on playing cards. 

It cost all of $1.50, so bargains are still around if you look. The owner would not sell a blue THOMAS U-282A hat for $2.00 when I dickered below the $3 sticker. He said he'd keep it and put it in his collection(??). 
Errol Q. Bond 
Fullerton, Calif. 

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Dear Errol: 

That's a nice Imperial, and the Sim U-927 would be close enough. There are numerous minor variations in all these oldies, both the glazeweld and one-piecer versions. 

The Imperial trademark in the book isn't quite complete, since I didn't have a specimen with a nice clear marking when I made the drawing. The extra couple wiggles inside the crown appear to be fleur-de-lis, but until you mentioned it, I never thought to note on many specimens since 1971 the exact character of these elements -- and still can't see them clearly on any specimen I have now. Maybe a reader can help us out if he has a specimen with a very clear marking, a magnifying glass and some artistic ability. 

Incidentally, I never came across this trademark in the registrations, but then I guess anyone can state it as a "trade mark" without registering it at the Patent Office. Yes, how sweet it is! You can come unto some real bargains when sellers don't take the trouble to first check in a book or with some acquaintance willing to help in pricing before parting with items, and this is even true at insulator show tables! 

At a flea market I once saw an ordinary porcelain beehive with a $3 sticker on it. Next to it sat another insulator with a $1.50 sticker on it, and he said he'd take a buck for it. So I paid him the buck and walked away with my THOMAS transposition -- and a little smile on my face. 

Jack

Last summer Matt Grayson (Roslyn, NY) suggested an idea that we might crack the date code used by Pittsburg High Voltage Insulator Co. in the 1915-1921 period if we recorded enough of the "date control" markings on specimens and then consulted the calendars for those years. The assumption would be that the work dates were probably not Sundays, and also maybe not even Saturdays. The table below is an update of our project on this showing all date stamp markings which have been reported thus far. 

I've seen many of these dated Pittsburg specimens in collections and on show sell tables in past years, but we simply can't have hope for success in this project unless each reader will take the time to send us a postcard reporting the date control stampings on specimens they have! 

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Dear Jack: 

In response to your request for help with an answer, here is some information on Frank Shore's interesting item as pictured on page 24 of the October 1979 issue of CJ. T

he device is correctly called a choke coil. The picture is upside down because the insulator petticoats are turned up; this choke coil assembly would be mounted underhung. Some are upright as shown, but the insulators are reversed with their petticoats downward. These are connected in the circuit as shown. in my sketch (copied below). 

When lightning strikes an overhead line, a very steep wave front travels along the line and causes insulation failure in equipment such as transformers or motors connected to the line. The choke coil has low inductance to the 60 cycle power in the line but offers very high inductance to the steep wave front of the lightning surge. This causes the voltage crest to be chopped down as the wave enters the choke coil and reduces the stress on the insulation of the connected equipment. A lightning arrestor is usually connected on the line side of the choke coil to discharge the lightning surge to ground, and the choke coil reduces the surge voltage entering the station bus.

It has probably been 50 years since a choke coil has been installed, and it would be hard to find any in use today. They were still shown in the 1929 Electric Service Supplies Co. catalog, and other electrical manufacturers also made these choke coils. 

The reason that their use has been discontinued is that when they were connected to equipment or a bus with metallic sheath cable, a resonant condition could exist because of the capacitance of the cable and the inductance of the choke coil. This would then cause excessively high voltages to build up across the cable and choke coil, thereby defeating the purpose of the choke coil. 
Frank Donnelly 
Menlo Parl, Calif. 

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