These are three pieces of a " old spark plugs" collection I inherited from my father-in-law. Seem to be rare. The #1 and #3 are quasi totally made of brass. The insulator of the #3 comprises hundreds of round mica sheets stacked on top of one another... And all of three can be taken apart almost intirely for maintenance. I guess they could date to around 1900-1920, but I'm not sure at all. Any information would be welcome. Thanks...