Has anyone else stumbled upon these special star caps?
I was awakened in the middle of the night by someone who told me he'd been following me, and that these special caps lead to some secret treasure. He also said to watch my back if I intended to keep collecting these star caps, because some waster was killing people for them.

There's something about it, I don't know what. I encountered a guy being attacked by a woman. When he killed the woman he told me she attacked him once she found out he made a necklace out of several of those.

Fun fact, when I first encountered them, the woman was running away screaming for help from the guy. Apparently if she starts losing, she tries to trick others to help her.

Yea, I'm with you. Can anyone give any insight to these star caps? I'd found a couple, and then I randomly came across some guy in the middle of the desert and he said he had a necklace made of the star caps, so I killed him obviously..haha. I have 11 of these star caps, but no one has come up to me at any other point. Has anyone found a use for them? Someone to buy them?

Sunset Sarsaparilla side quest. Collect 50. When you turn them in you find out there is no Great Secret Treasure, but you do get rewards. 1500xp, a Deputy Badge, and a Pew-Pew Laser Pistol.

That is, assuming the guide is correct.

I don't have the guide, but it looks like it is correct.
More under the spoiler...