This style is a carrier circuit insulator used for long distance telephone lines and was used in conjunction with a special steel pin with a lead lining (hence the "C" for Carrier Circuit and "S" for Steel pin; the meaning of "A", "O", and second "C" are unknown.) This style was also assigned the No.22CSC style number in 1942-1944, but no specimens exist with this style number.
4" H x 2 5/8" W
CS, CSA, CSC, CSO, E1
Rarity Scale (1-10):
Extremely Common (1)
Telephone Long Distance
Hemingray E1 Style
This is the earlier Hemingray E.1. style. Note the flared skirt, lip on the lower wire ridge and the extra threading inside of the skirt. This style is found in the  and  embossings.
Hemingray CS Style
The Hemingray CS styles are always embossed with the Owens Illinois logo: . This style has almost identical mold features to the E.1., but has no threading inside the skirt.
 Experimental Style
This particular variation has four hemispherical indentations in the base of the insulator (basically the appearance of four inverted round drip points). This is listed as . It is considered an experimental piece.