Yes there was, I believe the early models (1997-1999) had a closed caseback (see photo of ref. 5160 below). For 2008, PP has changed the sizing and layout of the watch meaning a genuine caseback from the early incarnation would not fit. That is, if you could get your hands on such a rare part. I also strongly doubt you could get your hands on the crown of a 2008 Patek Philippe aquanaut. Even as a genuine the watch is a poor seller - starting price is roughly $17,000 and it's stainless steel and rubber and fairly readily available. It's the ultimate "throw your money in the garbage" expenditure.
Also, I don't rightfully understand why so many of you are yelling "wrong date font" - I would say it's a tad too small, but I'm not going to judge until it spends 31 days on my wrist.
1999 Aquanaut