I used them in my office with a pair of Maggie Minis. Sequential serial numbers, made in the USA! One of the toggle switches was replaced some time ago, the replacement switch toggle is a bit shorter as seen in photo.
Works great and sounds sublime. The item "Rare Cary Audio CAD-80M Tube Monoblock Pair Original Cary USA 6550 Output Tubes" is in sale since Sunday, May 3, 2020. This item is in the category "Consumer Electronics\TV, Video & Home Audio\Home Audio\Receivers & Amplifiers\Amplifiers & Preamps". The seller is "handyman28" and is located in East Brunswick, New Jersey.
This item can be shipped to United States.