I purchased a used Balance 20 on Ebay. It looks like it has never been used. It is a version one hardware and made in Taiwan. Firmware version was 5 point something. It works perfect. But I had problems upgrading firmware.
I solved the firmware upgrade problem by doing the upgrade in two steps. I first upgraded to a version about half way to the latest. Then upgraded again to the latest version. It was trial and error getting the first upgrade to work.
Just wanted to pass on my experience in case others have this problem.