Is something rare if only one exists? 
Infrequently occurring; uncommon.
In this case it's ONCE. Only once.
This was Christenson's LAST Walker blank. This is Christenson's ONLY 8'8 Simmons. That's pretty uncommon. More than rare. Will not happen again. One of a kind is what I mean.
Is it nice? Well, he really wanted to keep it for himself.
