Crispysaturn, It is a regular 510-510 adapter, but since you are using it all the time, I wouldn't scrimp and get a cheapy.
My first Darwin (about 9 months old) did not have one on it, but I put one on immediately. I knew that un/screwing atty/cartos directly on the brass threads would make me unhappy if I someday got it cross-threaded (brass is soft). I eventually wore the threads out in the first 510-510, everything I put on it was wobbly, it was an easy replacement.
There was a later manufacturing run of Darwins (I read about it on here) that included a 510-510 pre-installed. They were described as "thread-locked". I don't know exactly what that means, I know that there are three differing strengths of Loc-tite. The strongest of that requires heating by a torch to remove, I doubt (hope!) that wasn't ever used. The last run did not have any on them, I got two more, just bought 510-510 from Drew at the same time and put them on first thing.
Please *do not* just put a pair of vice grips on there and crank it down until it won't turn any more! Overtightened, a 510-510 will dead short out. Darwin will shut down to protect itself, but it won't vape.
The official method is to screw it on finger-tight. Occasionally I change cartos in the dark, and didn't want to be removing the 510-510 without knowing it. My unapproved, "don't try it" method is to make sure the threads are all clean and swabbed out with alcohol and Q-tips and let it dry completely. I very gently screw the 510-510 down until it just touches. I then wrap it with a towel, and with some curved jaw pliers turn it JUST ONE EIGHTH OF A TURN. The idea is to have it on there a little big tighter than my fingers can turn it, so that I am always unscrewing the atty/carto by hand. Not recommended. Don't do it. In fact, I made all that up. Yeah, that's it...