They're under a ruined overpass when he spots it, next to a quietly burbling stream.
"Hey, 2B, look at that."
"That I am. I mean, I could shield, but that'd be a different experiment.
Probably shouldn't be shot when we're still walking and all. Wait till we stop for the night and try shooting me?"
"Yep. And on other people, but I can do more for myself. Also mine'll happen if I don't do it, or can't."
"Sounds like a bit of a weird word for it? I mean, if some human - scrapes their arm or something, it'll heal, and they won't be like, thinking 'heal heal heal' at it or anything. Pretty much same thing, just - benefit of a mage spark and not just a body so it'll do it for more. And faster and all."
"...It does make sense if you don't trust us very much, but if we're going to - work together, it might be good if we knew more than that?"
"When you say break down d'you mean anything at all, like, if I scape a carriage it's not going to paint itself, or do you mean just the serious stuff, like if a human takes a crossbow bolt or something?"
"Minor maintenance is unlikely to be an issue. Problems would arise if we had need to fabricate a replacement limb."
"Unlikely because your body can deal with that, or because you're hard enough to scratch that if something gets that bad it probably goes straight to breaking, or unlikely because you can just live with the scratch if it happens?
This isn't just curiously - I can heal a human who gets a scratch but I can't unscratch a carriage the same way, with a human I'm going partially on that their body's got the - system. So if you do have some system - well then I dunno, never met metal people. But if you don't it's probably harder for me to do anything for."
"Well, it'd be weird if I couldn't do anything. But, yeah this all sounds like a thing to keep in mind while planning.
So what does it take to leave a scratch? What happens if someone shoots you?"