Found a nice Milk of Magnesia bottle while metal detecting yesterday. Picked up a few ... - Reddit

That's a porcelain cleat. They were used in older knob and tube wiring. Great finds! 3.

from Google Alert - metal detecting great finds https://www.reddit.com/r/metaldetecting/comments/qnqafh/found_a_nice_milk_of_magnesia_bottle_while_metal/