Although the following items aren't exactly "screw-top Bostons", I thought collectors might be interested in the four patents covered this month. 

Below is the patent issued to John Garity of East Birmingham, Pennsylvania. I know of one of these insulators in existence. It is like figure one below. The present owner is unknown to me. As near as I can remember, it was originally located in southwestern Pennsylvania. It's interesting that Garity states in his patent application that the manufacture of similar insulators was previously attempted by others. He may well be referring to the S. McKee item on the following page, which is the same Samuel McKee as the CD 731 S. McKee & Co. Although, to my knowledge, none have been found, I feel very strongly that the 1870 McKee patent was produced. 

The third and fourth patents shown here represent similar attempts to produce this type of insulator. These two, also, have not yet been located by collectors. 

If anyone has any of the four insulators covered, or another of the same type, I'd like to hear from you, so that we may put additional information in a future column.