The known watches have all come to market somewhat recently and scholarship on these has been evolving. On all three,
link the reverse of the dial is signed in a similar fashion by Beyeler, a Rolex dial supplier of the
link time, leading to the theory that they all belong to the same, presumably small, batch
link and were produced at the same time. This case, dating to 1976, is the earliest known so far but the others date to just a few years later.