Young people today may not know what this is.
Answer: This is a mechanical pencil lead.
Other comment
Pencil tips that once used up, pull the tip out & press it into the back of pencil so another tip comes out. Pretty cool at the time
I remember the other pencils that had a big piece of lead that you just kept adjusting down and you never had to run out of lead with that from school either I still have one of those kind and some of the big long pieces of lead or graphite I don’t know what they’re made out of but they’re not real bad