16" bottle with pinched base, 10" neck and bright green glass....old(?)

Hello,
I was hoping to gain some insight on the possible age and purpose of this (seemingly old) bottle.
All four sides of the base are pinched, or so I'm told. On the inner lip, there are marks in the glass that indicate the use of some sort of stopper. The black coating or paint seems a bit unusual as well. It does not chip, peel or flake off but will rub away with a fingernail. The glass is bright green.

Height (top to bottom)- 16"
Neck length- 10"
Neck circumference- 4.5"
Top (lip) circumference- 10"
Base circumference- 19"

I really like the green glass underneath but don't want to make any changes until I know more about the piece. Any help/info would be much appreciated!

Thank you,
Rachel