I acquired this descender from Speleoshoppe at the International Congress of Speleology in 1980.
The Tokyo Top is 175 mm. high, 100 mm. wide, 16.6 mm. thick, and weighs 180 g. Both sides are stamped "Descendeur Top." Below this, one side is stamped "MADE IN JAPAN," and the other "TOKYO TOP PAT.P." A previous owner added "TINKER 9508R." The shape of the device is difficult to describe, so I will omit most of the verbal description and let you look at the photos. The only thing not clearly visible in the photos is that the center portion is thicker (16.7 mm.) than the upper and lower portions (11.2 mm.). The device appears to be forged out of aluminum.
I was fortunate that Ian Ellis gave me a slightly used version of this descender. At first I was completely unable to determine the proper, and safe, way to use this device. Since my descender was used, the wear marks showed the correct rigging. My error was in assuming it would be safe.
The device gives the rappeller an impressive 360° view for every few meters of the rappel. Unfortunately, the whirling scenery cannot be enjoyed because of the attention required to ensure that the rope and the device remain in contact with each other. The rope passes around the upper hook in a fairly secure fashion, but not so for the lower hook. If the rope comes off the lower hook, it can easily unwrap itself from the center guard prongs, leaving the rappeller with a 3/4 wrap around the upper hook. The resulting friction is not significant.
The device might be safer than it appears, but I am not willing to use the device in the field where I could accumulate enough reliable data. My assessment is that the Descendeur Top should be reserved for collectors only.