Richard Dobing from Bath, Ontario discovered this previously unknown embossing. This CD 120 has RD No 156417 embossed on the front skirt and a number 9 on the back skirt. This is now the third known insulator with the RD Number on it, the other two are CD 133 RD No 154745 and the CD 126 RD No 149959. There is also a fourth RD Number for the yet to be found CD 134 RD 154744

What does RD stand for? RD is an English Registry mark.

Reprinted from “INSULATORS - Crown Jewels of the Wire”, October 1975, page 28

“On May 22, 1890 a number RD 149959 was issued (for the CD-126 style) to Glass Merchant James Bridger, Mead House, Upper Edmonton, London. August 20, 1890 RD No. 154745 (CD-133) was issued to F. H. Davey & Co., Edmonton Glass Works, Upper Edmonton, London. Also sent to me were photostats of the original drawings of the insulators as they were presented for registration. They included another insulator, RD 154744 (a CD-134) which to my knowledge has not been found, at least not in this country.”

The recently discovered CD 120 was found in Ontario, Canada

The CD 126 have been found in NY, NV, GA,

The CD 133 have been found in CT.

Location data from:
Geographical Locations of Glass Insulator Usage in North America

Photo Credit:
CD 120 Richard Dobing, CD 126 and CD 133 Dwayne Anthony