It could be hone wear, but that is usually accompanied by similar changes on the bevel (wider bevel and the bevel closer to the spine aka reduced blade width) which I'm not seeing. It could also be from uneven grinding. It could also be from restoration work - properly done to correct/hide issues or incorrectly done and therefore causing issues.

I'm assuming this is an auction you're thinking of bidding on, and thus don't want to share full info, but it's hard to tell from the single poor photo.