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String of suspension insulators"Suspension" and "Strain" insulators are the same thing; when used in the vertical position (with the conductor hanging below), they are called "suspension". When used in the horizontal, to dead-end a conductor, they are called "strain".

There are two basic types of suspension insulators: unipart, and multipart. Multiparts are very rare, and there are only two known styles (Cochrane Bells and the Hemingray type). They were used around 1900 to 1920 only, and were for substation use. Uniparts are the common style, where each unit has a single piece of glass, a cap, and a pin, and the units connect with each other cap-to-pin to form any length chain.
A Proposed Numbering System
I propose an S-numbering system for glass suspension insulators. The system is keyed primary off the glass shell, with a suffix to indicate variations in the metal cap and pin.

To make the system more mnemonic and useful, the numbering would be S-DDNN where DD is the diameter in inches of the shell, rounded down to the nearest inch. NN is an arbitrary sub-code to distinguish the individual styles near the same size. Within a size, numbers are assigned in petticoat order. That is, the fewer skirts, the lower the number. "Bell" or "aero" type glass, with just a single outer shell, would come first. Complicated "sombrero" types with numerous inner skirts would come last.

Since the smallest size insulators is about 5", that leaves the lower range of numbers available for multiparts and other uses. I would put multiparts in the 00NN range, and leave 01, 02, 03 and 04 for other uses (radio strains?).

Multi Suspension Table
S-#### Maker Style# Shells Width Length Weight Color
S-6 Cochrane 6 6 25" 16 lb. Purple
S-10 Cochrane 10 6 ?" ? lb. Purple
S-50 Hemingray 5 6¾ 22" 15 lb. Aqua
Unipart Suspension Table
S-#### Maker Style# Width Shape Skirts Hardware Weight Color(s)
S-5## Sediver 5" Disc 1 Clevis 2 lb. Aqua, Off Clear
S-5## Sediver 5¼" Disc 1 Clevis 3 lb. Olive Tint
S-6## Pyrex 65221 6" Disc 3 Clevis 4½ lb. Clear, Clear w/Carnival
S-6## Pyrex 65241 6" Disc 3 Hook 4½ lb. Clear?
S-6## Pyrex 65251 6" Disc 3 Clevis+ 4¼ lb. Clear?
S-6## EIV 6¾" Disc 3 Ball 4 lb. Aqua
S-7## Pilkington 7" Disc 3 Clevis 4 lb. Ice Green
S-7## Pilkington 7" Disc 2 Clevis 4 lb. Light Yellow Olive
S-9## Pyrex 9" Disc 4 Hook 6 lb. Clear w/Carnival
S-9## Pyrex 9" Disc 4 Clevis 5 lb. Clear
S-10## EIV 10" Disc 4 Clevis 8 lb. Aqua
S-10## EIV 10" Disc ? Ball 8 lb. Aqua
S-10## EIV 10" Disc 3+ Ball 13 lb. Aqua
S-10## Sediver 10" Bell 1 Ball 9 lb. Aqua
S-10## Sediver 10" Bell 1 Ball 8 lb. Aqua
S-10## Sediver 10 1/8" Bell 1 Clevis 10 lb. Aqua
S-10## Pyrex 65234 10 Disc 4 Ball 8¼ lb. Clear
S-10## Pyrex 65244 10 Disc 4 Clevis 8¼ lb. Clear
S-10## Pyrex 65216 10 Disc 5 Ball 12 lb. Clear
S-10## Pyrex 65226 10 Disc 5 Clevis 12 lb. Clear
S-10## Pyrex 65214 10 Disc 4 Ball 8½ lb. Clear w/Carnival
S-10## Pyrex 65224 10 Disc 4 Clevis 8½ lb. Clear w/Carnival
S-10## Russian 10 Disc 3 Ball 7 lb. Light Blue-Aqua
S-11## EIV 11¼" Disc 4 Ball 12 lb. Aqua
S-12## EIV 12½" Disc 5 Ball 21 lb. Aqua