You forgot the Leap Years.
That would make it 3,652 rifles.
And while the Ban is gone Federally, six States and DC still prohibit them.
So I don't think it would be all that worth while.
But if somebody DOES think it's a good idea, how about this:
The serial number has a date when the Ban was in effect.
Like this: nnn-091101.
The n represents a number from the Manufacturer, the 091101 stands for September 11, 2001. The Ban was in effect that day. And that rifle might sell for extra in honor of that day.
Thinking it along a bit more; 3,654: The Last Pre-Ban and the First No-Ban.