Vintage Find- What is it?

The other day while at my late father in laws estate, I seen this large pin laying around. I picked it up and smiled. The first thing that came to mind was how in the 60's,70's or 80's the girls would wear plaid wool wrap skirts. The fad was to wear a large safety pin on the skirts, not only to make a fashion statement, but to also hold the wrap together so we didn't show our draaawls.
This pin reminded me of those days.

Not doing the math, but I actually wore one. However, I come to find out, this is not the same kind of pin. "Yea, I thought it looked pretty old".

So, What is it?

I posted the photo on Facebook to get peoples response to if they remember what this pin was used for and here are a few of the responses I got.

My daddy guessed: 

It was an "Apron Pin"

One facebook friend said: 

It was a "Locker Pin". 

"They used wire baskets at the public pools to put your personal belongings in. 

The pin had a number that identified your locker basket".

Another Facebook friend suggested: 

It was a "Coal Miner's Pay Pin". 

"Miners would shovel coal into a coal car. When it was full, he would attach his pin to the car. 

When the ponies pulled out the cars, the miner, who's pin was attached, was paid by the car. 

Each miner had his own number".

I found all these answer very interesting but the locker pin sounds more like it to me as it was suggested more than once. But they all could be wrong or they all could be right...

Do you have any other ideas what this pin was used for?