GC might refer to Guangdong, China, where they may have been manufactured. Without knowing anything about them, I would only use them in regulated 18650 mods like a Provari or Innokin Cool Fire 1.
"Without knowing anything about them", you still give a recommendation to use them in a mod?
Who can say whether these purple mystery batteries are ICR or IMR batteries? Or even if they are lithium batteries for that matter? (They could be non-rechargeable alkaline batteries for all you know.)
A Provari uses only
button-top batteries, not flat top like the OP says these purple batteries are. A Provari is a regulated mod like the Innokin Cool Fire 1 - both which require
high drain batteries for the buck boost circuitry of the processor. I still don't understand where the idea came from that you can put any kind of battery in a regulated mod because they have "built in protection circuitry".
This is just wrong.
Never assume that a random vape shop salesperson or internet vendor knows enough about batteries to sell you the correct ones (safe & appropriate). I've read of vape shops selling mechanical mods topped with a
sub-ohm RBA's with
low-amp batteries; I've read of China distributors equipping mod kits with
unprotected ICR batteries. Whoever is putting these setups together obviously do not know about batteries or safe battery practices.
Never use "just any kind of battery" in a mod. That is dangerous not only to yourself but also others that live with you.
BATTERY BASICS FOR MODS: IMR OR PROTECTED ICR?