If any of you have wondered if T12 tubes shorter than 8 feet existed in Japan, here is an example of a 1960s National 580mm FL20W tube on youtube:

https://youtu.be/oIgdnyn30XQ?si=kf6OdG8SFSAQ2Chp

In Japan, they tend to denote fluorescent tube diameters in millimeters instead of eighths of an inch like most of the world does. For example, they refer to T5 tubes as “15.5mm” tubes, T8 tubes as “25.5mm” tubes, T9 tubes as “28mm” tubes, T10 tubes as “32.5mm” tubes, and T12 tubes as “38mm” tubes.