Is there a reason you need the actual model number? You might be able to find one listed on eBay that shows a photo of the model number tag, but I suspect you are looking to buy a replacment from somewhere like eBay and want to make sure you get the right one.
There may have been multiple versions of the deck you describe based on if you have the subwoofers and amp, etc. However, I think the 6-disc non-navigation system was the same for a few different grades of system. The difference was the number of connectors that plugged into the back.
These may offer the information you're looking for:
1,
2,
3.
-Rod