20000 Item #'s => Proto 2000 Engine Age?

[Anonymous]

I see quite a few older Proto 2000 engines at shows, many in newly packaged condition.  While researching I've noticed many of the currently offered engines have product numbers in the 30000-4xxxx range (Gray boxes?).  While many of the older enginers have product numbers in the 2xxxx range and blue boxes.  Can the product numbers of these engines be used to estimate the age when these engines where initially released.  Can the same be said for the color of the box (brown, blue, gray, etc.)?

[arkansasrailfan]

Yes, that is one way to do it.