They look like capacitors. If the house dates back to the 50's or
older they may have been part of an external telephone bell. They
may have been installed as a radio canceling device to filter out
radio broadcasts on telephone line.
It could also be a crackpot customer device. These were various pieces
of telephone equipment installed to do absolutely nothing but satisfy
a chronic complainer. It would be a special/secret device that nobody
was supposed to have.
Believe it or not those devices actually worked. :)
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.