That's a Grumman Goose - G21
Buffett used to have a Widgeon, (which he crashed on a water landing in Miami) but he now has a 'new' Goose, and a couple of other airplanes. The Goose is the 'big brother' of the Widgeon and the Mallard is the big brother of the Goose. I have an old wooden Widgeon propeller hanging in my house.
The last Goose was built in 1945.
Its a beauty of an airplane - I had the opportunity to ride one this past summer.
The livery of the Goose in the photo is the one I chose for Danika's Buccaneer's Bliss in Sunset Negril.
Here's a YouTube of my Goose ride:
