Interruption in canning process
I would not keep it or eat it and just consider it a loss. That is a long time for the food to cool down/seal, etc. The processing time is usually carefully calculated so that the core of the product in the jar gets to the proper temp. With the processing time only being 10 mins it would mean only the jar and maybe a small amount on the edges would have gotten to 240 deg F. 

I suppose it could make a difference if it was a hot pack vs. cold pack, but I would still not risk it.

Since you're an experienced canner, I assume you already know that it's possible to lose pressure during the process and then restart the time when the canner gets back up to pressure, but that is usually a few minutes at most, not hours.