Such heavyweight insulators as these may date all the way back to the 1850s when they were produced for telegraph lines. Little by little as different technologies emerged, insulators were even more necessary - for telephone lines, electrical power lines and more.
There are thousands of collectors who have researched and indexed the individual insulators and their use. Some are quite valuable while others are just valued for their artistic appeal. In fact, we've seen ashtrays, votive holders and ornaments made from insulators buy just adding chain, charms and a bit of creativity.
Porcelain insulators were never good for communications, but worked well for power applications. Glass insulators worked for both. Some of the oldest ones are just gorgeous.
Our abundant grouping came to us via our good friend, Harry, whose father collected them throughout the eastern United States (and perhaps, beyond, Harry was not completely sure). Harry is now 90, so we can only guess at the age of the collection!
We have not sorted through these or researched them, so yours may well be a gem or a dud. It might be glass or porcelain, made in the USA, Canada or elsewhere. We have seen some sell on eBay for upwards of $300! Now, we have no idea how valuable any of these are. We're selling them as is. Yours may show a bit of wear, or, indeed, it may be pristine.