I was visiting with my grandmother today in her greenhouse as she was working. I notice on the wall a smaller version of the same device in the original post. I say, "Please tell me what this thing was used for"; knowing she would know or the thing wouldn't be in her greenhouse.
Her reply, "We used it to muzzle the calf so it wouldn't milk".
hmmmmmmm, - "So what is the larger version for that I found in your parents house?"
"The HORSE", she replies.
Whether it was designed and intended for that use or not - it was certainly used that way on this farm.