Serial date vs. Purchase Date

[deepseadweller74]

I'm in the market for a 118238. My confusion lies with the serial date vs. purchase date. Last week I visited a local dealer. He showed me a 118238 with a D serial (05-06) but not pre-owned. He purchased from another dealer who lost ability to sell Rolex watches.

I also see similar thing here in classifieds, i.e. D serial but purchased in 2010.

Few questions: is it possible for a dealer to have a watch sitting in the case for that long or is there another explanation? As far as purchasing, is the actual purchase date a better meter for the condition of the watch than the manufacturer date? Should I be suspicious due the discrepancy in years? Thanks, everyone.