Stan, yes it is threaded. I took that mount off a historic home I worked on in the '90s. Had that lying around all that time, and also had a variety of insulators I had gathered. The mount takes huge flatheads that I never had big enough any time I'd be motivated to hang it up. Finally one day I ended up with a couple big-uns and hung 'er up! I have a bunch of clear insulators and wooden mounts, too. So the one you have, is it ceramic or glass? I knew people collected them, but had no idea of the values.
I never heard of putting glass out to change color (You pullin' my leg?). But I think glass is cool, especially colored, even in a pile. I walk my road and keep the trash picked up while I'm at it. One day it hit me to pile the cans, glass, and plastic bottles in a clear spot just beyond where the county mows. One, it saved me from carrying it all the way back home. Two, it started looking cool as it piled up. I try to keep the colors glass/plastic on the outer area. Three, maybe it will make the people who still actually think the world is their trash can to spark a trace of conscious thought. Funny thing. Once it started piling up someone took the aluminum cans
, so I keep those for myself now. Once, someone came along and picked it all up. I count that as a success. Four, I wanted to see how big and high of a pile it makes to show people how it all adds up.