I agree that it looks like an OEC from the photo. Shape is off-round and culet appears to be off-center (at least looks that way from this one pic). Neither of these things would be a deal breaker for me if the diamond is lively and in good condition. It''s very difficult to judge the potential beauty of a stone from one photo - can the seller send you additional pics and maybe a video clip? If there is a good return policy and you think the price is fair, I think it merits consideration, but ultimately it has to speak to you!
I would think OEC as well with a slightly off round outline. Have you asked about the condition of the stone and ring? Sometimes old cut stones have chipped girdles.