Original Item: Only One Available. Here we have something that we have not had before, and did take a bit of digging and hand-writing Japanese to identify. This is the optical sight for the main 37mm gun of a Japanese WWII Type 98 Ke-Ni light tank. There is not much information on these, and also very little on Japanese tank sights in general, so we are relying on the description on the box, which is marked on the top with:

This translates to "Type 98 37mm tank cannon sight container", which pretty much describes what it is. The inside of the lid and the data plate on the side are both marked with date 八 十 昭, for Showa 18 or 1943, with the data plate also giving the third month of march. 

The optic itself is marked as well on the side with the specifications and maker mark:

2×20°
(EK Star Logo)
37 No1048

Maker marked "EK" in a symbol that looks like a six-pointed star (like and elongated Star of David). “EK” stands for Enomoto Kogaku, which ceased to exist before the end of WWII, as they were bought out by Fujifilm to become Fuji Photo Optical Company in 1944. We checked the optics, and they are still mostly clear but definitely could use a cleaning. The range reticle / graticule is still visible, however the fabric covered rubber eye piece has definitely seen better days.

The sight is also marked No1288 on the side by the markings, while the transit chest is marked NO. 1 0 9 4, so we assume it may have been swapped at some point. However, the optic fits perfectly in the 15" x 3 1/8" x 3 1/8" box, so we believe it is correct.

A wonderful Japanese tank gun optic from WWII with some great research potential!

The Type 98 light tank Ke-Ni (九八式軽戦車 ケニ, Kyuhachi-shiki keisensha Ke-Ni) or Type 98A Ke-Ni Ko (also known as Type 98 Chi-Ni light tank) was designed to replace the Imperial Japanese Army's Type 95 Ha-Go light tank, Japan's most numerous armored fighting vehicle during World War II. Although designed before World War II began, production did not start until 1942, with 104 being produced by the end of the war in the Pacific.

History and development
The Type 98 developed in 1938 was a light tank with the same weight as the earlier Type 95 Ha-Go, but with thicker armor. The first prototype was originally known as the "Chi-Ni Model A" and completed by Hino Motors. The second prototype was originally known as the "Chi-Ni Model B (a/k/a the "Type 98B Ke-Ni Otsu") and completed by Mitsubishi. This second experimental model had a different suspension system with four larger road-wheels, similar to the US Christie suspension design. During field trials the "Model A" demonstrated superior performance, especially in off-road capabilities, so the Hino design was accepted However, the Hino "Model A" prototype did not enter production at that time. This can be attributed to the adequate performance of the aging Type 95 against obsolete tanks of National Revolutionary Army of the Republic of China forces.

With the start of World War II in the Pacific, the Imperial Japanese Army General Staff realized that the Type 95 design was vulnerable to .50 caliber machine gun fire and attempted to develop a light tank with the same weight as the Type 95, but with thicker armor A production contract for the Type 98 was awarded to Hino Motors. Series production began in 1942. A total of 104 Type 98s are known to have been built: 1 in 1941, 24 in 1942 and 79 in 1943. By the end of the war, the Imperial Navy had priority on steel for warships and aircraft construction, leaving the Imperial Japanese Army at a low priority for raw material to build tanks.

Design
The design of the Type 98, in comparison to the Type 95, featured thicker, welded armor of improved shape, including the use of a Mitsubishi Type 100 6-Cylinder air-cooled diesel engine, rated at 130 horsepower, and located sideways to make maintenance easier. The height of the tank was 50 cm lower in profile, and slightly lighter and shorter in length than the original Type 95. It could travel at 50 km/h (31 mph) even with its thicker armor. Three pairs of bogies with six road-wheels connected to the chassis using bell cranks, which transferred any movement in the bogies into sideways motion that was absorbed by springs. This gave the tank better stability over its predecessor.

In contrast to the one-man turret of Type 95, the Type 98 had a two-man turret, which offered more room for the gunner/commander. In the turret was mounted a Type 100 37 mm tank gun with an angle of fire of -15 to +20 degrees, a muzzle velocity of 760 m/s, and also a coaxial 7.7 mm machine gun. The driver was located in a central position of the chassis. To maneuver the tank, he used a standard steering wheel.