The CD27 is the largest end-view nixie tube made by Rodan-Okaya. At 54mm, the digits are larger than the NL7037, Z568M and R|Z568M.
This tube was used to display the speed for passengers on Japanese trains – see the photo below. It looks like there is also a tube the same size with Km displayed:
The tube is also used at the Tanegashima space center in the press room in a countdown clock. It looks like there may also be a GR-727 on the bottom left: