ALMOST the same model Dino, but not quite.
Zurf and Chris are right. Be careful Nao! From what I read, as of 2010 Martin started making ALL the 15 series from Genuine Mahogany (although I could be wrong, and MB may be right about it being 2011). Either way, when they started doing this they "changed" the names of the models to include the "M". I do NOT doubt one bit that the older models are EXCELLENT guitars, but if it's Mahogany you have on the brain, make sure you get the M. Also, the older model 000-15 has the CIRCLE dot inlays (as in that craigslist post) and the newer ones like mine have diamond dot inlays. The older ones have the paper model "sticker" on the inside such in the craigslist picture, the newer ones do not (the info is simply in the wood itself, no sticker to be found).
I looked all the differences up when I was buying mine to be certain that I was getting the REAL DEAL after Chris alerted me to the fact that many Mahoganny guitars are really sapele. So keep your eyes open. The older models went for around $700-800 new, the newer model will be found for $1100-1400. $500 seems a nice fair price for that guitar, and again I say... I am SURE it's a great guitar, but keep your eyes on the prize as it seems it's the true 000-15M you're after!
Good luck!!!!