They are porcelain. They are labeled as HEWLETT with a patent date. I have tried looking them up as "buttons" and "suspensions" but haven't located anything similar. Are they a type of "strain"? Just want to know what to call them. Thank you for your help in advance!

UPDATE: Identified as Hewlett Suspension Discs. Steve Coffman provided a great link to historical info about Hewlett. http://www.r-infinity.com/Hewlett/index.htm

Thanks to all that replied with an answer!!