I can't see the picture. Hope you can attach it.
How about size? And what color is it? Shape?
Now, large natural pearls do get astronomical prices at auction, but still... those numbers seem crazy.
It is fairly easy to get this type of references - prices realized by pearls at international auctions. And if you are looking for large, important pearls only, there really are not that many being offered each year. Allot in the high five figures, some higher. You'll see. You know your pearls while I do not, so it is up to you to select the right price reference.
Both Christies and Sotheby's make it very easy for you to obtain a rough valuation for an exceptional piece of jewelry from them. All you have to do is e-mail pictures. If there is interest on their side, you'll hear back with some numbers and perhaps an invitation to consign
They're good at this, believe me.
About identification. Yeah... you would be well served by a lab report. AIGS in Bangkok is fairly well known. SSEF or Gubelin or AGTA are the choice addresses for important gems. At least AGTA has a 'take-in window' in Bangkok. SSEF was planning one. Shocking as it might seem, all of these take in things by mail. If you trust your pearl might be of the six-figure kind, the cost of proper ID and valuation should be a trifle And the only way to go about such business... that I know of.
My 2c.
Hope to see the pearl!
PS. Hell if I know what's up with that 'Pearl of Allah' thing. Absolute record for a pearl item: 7m or so for the 'Baroda' necklace. Six times that is... just a random number on a piece of paper. 
The highest price paid for a pearl at auction was around $600,000 for a historic piece. There really are just a few market places where such prices are realized no matter what the object looks like.