The Japanese Type 97 Heavy Bomber entered service in 1938 and saw service in the conquest of Manchuria, the battles of Khalkhyn Gol (against Russia) and the earky stages of the Pacific War with the USA. The aircraft had an exceptional performance for the time but this was bought at the cost of limited defensive equipment. Heavy losses to better armed allied aircraft forced its relegation to training and a wise variety of second line duties. Like most Japanese aircraft types it was used for Special Attacks (Kamikaze) in the closing stages of WW2.
The spherical depression under the model is to mount it on a 6mm BB.