Wow!
When I posted my question I was thinking about really rare, rare guns.
It did not occur to me that everyone, including myself, has a Holy Grail desire which is unique to what they collect or shoot.
What lead me to post my question was coming across a statement somewhere, do not remember, which said the Holy Grail for Smith collectors would be a Smith revolving rifle which would sell for well over $20,000. I then wondered if it was a true statement. I did a search on line for sales of the 320 rifle and found several sold below $15,000.
I know any firearm owned by a noted personality could sell for, possibly 6 digits, perhaps more.
So, I guess there really isn't a True Holy Grail Smith firearm for everyone.
Thanks,
Marty D