This is a nixie tube made by Rodan-Okaya of Japan. It displays two letters, ‘A’ and ‘R’. There is no model designation associated with this tube and it does not appear in any documentation that I have found.
The envelope is clearly the same as the GR-201, so it is reasonable to assume that it has similar electrical characteristics, given below:
| Letter size | 19mm |
| Min current | 1.5mA |
| Max current | 3.5mA |