"Codes On Your Makeup"
"On the back of your makeup products, you can often find numbers like: "6M", "12M" or "24M". They represent the life of the product on your shelf after opening. So in the above example, you have about 12 months to use this face cream before you should think about throwing it out and replacing it."
https://www.amazon.com/Panef-Corp-Powdered-Graphite-Lubricant/dp/B0016GZQ60
Now I don't use hairpins but I would think the side WITHOUT the sharp pointed end would be better against your scalp?