I would literally be surprised if I could count 15 dives on this reg. I only used it while practicing in doubles when I intended to start cave training but never went through with it. The other dives are a few on which I let a buddy use the reg. The reg was rinsed after every dive..if you are local and want to meet up you can see the rest of my regs, years older than this, with no corrosion.
Last year, I lived in an apartment complex that had chinese drywall..since this wasnt a reg I normally used, the reg was stored in my bedroom closet for some time and the chinese drywall is what causes that weird green corrosion to metal (obviously wasn't aware of this issue until after the fact). Google chinese drywall if you're not familiar and you'll see examples. Service the reg, clean off the corrosion if desired and its a perfectly fine working regulator.