I'm only concerned about the real ones....
There have been isolated cases of forgery in the past, but those instances have been rare. OA is actually not that easy to fake, as there's a published counterpart anyone can use for comparison. It's not easy to copy line-for-line, at least not freehand. Plus, anyone who's familiar with an artist's work can spot inconsistencies, when it comes to unpublished pieces.
Which is not to say that OA is foolproof. As OA becomes more valuable and brings more outside attention, this sort of thing is inevitable. For now, the odds are low, but always good to keep a watchful eye.
Dude-- congrats on the page. For anyone thinking that was expensive, I can tell you right now that was a steal and an absolute no-brainer. It would've been awesome to have two back to back pages together from #1, so I am super jealous.