Help identifying movement in Planet Ocean

Hello All. I've been lurking on the forum for a while now, but just purchased my first Omega last week... bought a "NOS" Planet Ocean 2500 (2200.51.00).

I purchased the watch from an individual who bought it from an AD in October 2015 (but never wore the watch). I am trying to determine what the movement is. The seller indicated that based on his research, it is the 2500 "D" movement, but I would like to confirm. The serial number is 85254038. I have searched online but have not found any good sources. Any help would be greatly appreciated... thanks in advance!

The consensus is that anything with a 8525xxxx or later serial is the 2500D. I don't believe that omega has ever issued anything official on this though.

Thanks, BGATOR. That's very helpful. I knew the watch was later production for the 2500 movement, so assumed/hoped that it was the D movement. But thanks for the input!