Many thanks for your kind compliments on the howitzer! I really appreciate them! I had never seen before until I bought it. It's a new model, just released this year. I think it's meant for Japanese market only since its instruction sheets are in Japanese only. I bought it from a fellow modeler who got it from Japan. I paid $60, not cheap. It would cost more if ordered from Japan.
The instruction sheets though in Japanese, provides some history in English:
"Since the Meiji Restoration, Japanese artilleries had depended on foreign products. In 1881, the Imperial Japanese Army decided to produce a howitzer on its own. The Osaka Army Arsenal, which took charge of its production, constructed a prototype referring to Italian 28cm howitzer. In 1884 the first prototype was completed. A test fire for checking accuracy was conducted at Shinodayama, Osaka in 1986. As the test fire proved excellent, the artillery was officially adopted in the next year.
In Russo-Japanese War, which began in 1904, the 28cm howitzer was mobilized. In the seige operation of Port Arthur including the battle of 203 Hill. 18 howitzers participated. The Army finished the construction of emplacement in only nine days, which commonly tok as long as three weeks. The six howitzers gave a heavy blow to the enemy. After seizing the hill, they also made a shelling against the Russian Pacific Fleet into submission, contributing to Japan's victory in the war.
The 28cm howitzers continued to be used in subsequent wars. In 1930s the construction of the emplacement and the traction were further advanced. The howitzer became capable of being towed by the 13-ton tractor, though at the speed of 13km/h. When the Kwantung Army deployed 12 howitzers at the shore of the Amur River, they were capable of opening fire in only twelve hours."
(the text ends there)
Some figures and my guess:
280mm - gun's caliber figure
2.863m - probably barrel's length
10,758Kg - probably weight
-10 - +68 - probably angle of gun elevation
360 - probably rotation (full)
217Kg - probably weight of shell
142-314m/s - probably velocity of projectile (metre/second)
7,800m - probably range of fire