They were bought at Kinki's online shop in July 2021
My own feedback about this amplifiers is here: https://www.kinki-studio.com/post/army-tank-and-swiss-luxury-watch-ex-b7
For possible very very rare after sales services, the blocks are "lego-type", Kinki has a lot of online videos for changing parts, and updating anything is straightforward and very easy, even if you are not a DIYER.
You can find a lot of online reviews as this one for exemple: https://www.magazine-audio.com/kinki-studio-ex-b7-mono-blocks/
Contact seller: TNK
All classifieds from TNK