That's the exact reason I started this thread.
I initially purchased a 1960 plate for my Impala. When I went to the DoR to register it, the plate was denied due to the number/letter pattern. It was LNN-NNN.
Although it was legit in 1960, the computer rejected it because that pattern is now reserved for Dealer's plates in MO. There are several other patterns that are now reserved. So, just because a plate was ONCE-UPON-A-TIME legit doesn't mean is is CURRENTLY legit. That was a $100 lesson that I didn't want to see others repeat.
If I need to further clarify my initial post, please let me know.
-Kevin