Maybe a old ground strap for a old radio/TV ? Seen something similar on the floor of a TV antenna station out in the sticks I delivered bottle water to many years ago. Just a shot in the dark.
If I remember, the business end was painted blue, at least that was what it looked like when I trained it went flop out the tube! Don't remember to much I was to busy eating dirt.
Your going to want to be cautions with full glass bottles, many decades ago I delivered those bottles, and they will blow apart ! Take into consideration they were designed to hold water at 8lbs per gallon, 75 to 100lbs of coins will make them blow out. One of my customers almost lost a foot...