My father also collected them when he was a young man in the western US serving in the Civilian Conservation Corp prior to WW 2. There are literally multiple thousands of varieties that still exist. The vast majority, although interesting, were common and worth nothing. If you run a search for "collecting insulators" in the book section of Amazon.com you will find several books that list those that have some value as collectables. Otherwise, the value of anything like that is limited to what someone else is willing to pay to acquire it.