I picked these up at the annual Cornville 10-Mile Yard Sale today. That's right, virtually every house for a 10-mile stretch of road—and the cross streets—hold a yard sale. The traffic is awful, but there are some neat finds. Like these things. Anyone know what they are? I'm guessing either glass standoffs or some kind of wall tubes. They are 4" tall and about 3 ½" outside diameter at the top. The base is about 2 7/8" outside diameter, and the smooth hole tapers from 2" wide at the base to 1 ¼" at the top. [id=373481452] They were made using a three-piece mold, and each one has chipping around the inside of the hole at the top, much like the CD 190/191 bases, where there was a glass slug that was broken out of the top of the pinhole before use. These are each embossed on the lower front "ridge" R 5050. Any info is appreciated.

Answer: Apparently these are glass bushings used in substation control room switches and streetcar powerhouses to isolate an open switch from the switch panel as shown here by Dwayne Anthony: [id=224527531]. And they come in different sizes as shown here by Tom Miller: [id=345739515].

Thanks to Bill Ostrander, Mid Norris, and Dustin Logan for the info and links.