Hello all. I am new to this forum. I recently dug up several hundred old bottles (1930s-1940s) on my property, which used to be home to tennant farmers. One that really has me puzzled is a small, green medicine dropper (no top) that has a shape that is difficult to describe and has 2 raised bumps on a concave side of the bottle. I'm attaching photos. Can anyone tell me the purpose or significance of the raised bumps?

Sent from my SM-G950U using Tapatalk