The R|Z568M nixie tube is made by Dalibor Farny. Dalibor started making Nixie tubes in 2013, and for a long time was the only manufacturer of these tubes. Dalibor named his tube the R|Z568M, after the inspiration, the Z568M. The digits are the same size (50mm) and the pin-out is the same.

His tubes are made-to-order and can be customized to suit your needs. There are upside-down tubes, tubes with a copper anode, tubes with brass bases and black bases. Etc.