If you love a Hummingbird - a square-shouldered Gibson dreadnought - you might like trying my 1946 J-45 (a slope shouldered dread) or my '48 Martin D-18. Hummingbirds, J-45's and D-18's are classic models, but OP are you talking about models or specific guitars that are "the Best"? I realize that within any model line some unusually great guitars roll off the assembly line.
Finagle if your Yairi is in very good condition you can almost double your money on Ebay. I have a few Gibsons and love them, as well as a couple of Martins.
There is no standard location for the placement of the serial number, but it will always be one of the most prominently displayed pieces on the back of the banjo.
To prevent the serial number from fading, keep your banjo in a dry and moderately cool room.
Originally from a small town in the Midwest, Reilly now resides in Northern California.