The One Hertz is the foundational piece for the Gronefeld brand. It debuted several of their developments that have been used in later pieces: the stainless movement bridges, the push button crown from the tourbillon, etc. As the name suggests, this one features a huge dead seconds mechanism (one hertz).

Custom ordered with this stunning blue dial in a titanium case by GaryG, the delivery experience and full write-up of this piece (including Gary’s stunning pics!) can be found here https://quillandpad.com/2018/09/01/gronefeld-one-hertz-a-collectors-journey-archive/