My girlfriend believes that it was never there before. I think it's been there there all along, but it's now in sharp relief with all the rest of the muck (and there was a lot of muck) around it removed.
It turns out she cleaned the tub with liquid bleach, which we don't normally do. The question is, could the stain have been caused by cleaning the tub with bleach (meaning it is in fact new), or is it more likely to have been caused by the dripping faucet we've had forever and have neglected to take care of (meaning the stain was already there)? Or some combination of the two? And, finally, can anything be done short of refinishing the tub?
And yes, I now know that one shouldn't use bleach on the bathtub, but I'm still curious if a single application could cause something this serious.
Thanks for any advice; I'm definitely inexpert in this domain. Feel free to send email to ivanxqz at yahoo dot com (obviously subtitute "@" for " at " and "." for " dot ".