A genuine AOCo item from WWII [Author: Peter Jonkman - peter@archeo.nl]

Examination of a trench periscope made by Asahi Opt. Co. in 1944

Little or nothing is known about the products that were made by Asahi Optical Co. during WWII. Although it is said that the company was forced to produce optical devices for military purposes, I’ve never seen anything from that period in my 15 years of collecting.

Many of us know how good eBay is for finding rare items. Over the years, I was amazed by the large number of auctions for interesting Japanese military optical items from companies like Nippon Kogaku (Nikon) and Tokyo Kogaku (Topcon). Those items were often brought back to the USA as a war souvenir. This means that if AOCo really made military items during WWII, then eBay was definitely the place to find them. But no matter how hard I looked, none of the Japanese military items I found appear to have been made by Asahi Optical Co. So either AOCo never made military products, or they only made very specialized items in limited numbers.

Just a few weeks ago, I was lucky enough to track down a genuine WWII item from AOCo (thanks to an Olympus collector from The Netherlands, who found it in a large lot of microscope items he bought). And the item proved to be very interesting and unique!

The label
The item came in a olive-green case and that in itself is an indication of its military purpose. On the lid, there’s a metal label with a lot of Japanese characters and a serial number with Arabic numerals. Unfortunately, I am not able to translate Japanese kanji symbols. Thanks to the translation made by a Japanese woman (see acknowledgements section), I was able to make sense of it.

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First, we need to realize that Japanese symbols should be read from right to left. The upper row is, at places, hard to understand because some archaic and unknown ideograms were used. However, it more or less translates in "Type 93 50 [unit of measure] observation item using mirrors".

The second row contains the serial number 8411 and an unknown ideogram that probably could be the name of the manufacturing plant.

The third row contains the manufacturing date. The item was manufactured in the 19th year of the Showa Era (the reign of emperor Hirohito), which means that the item was made in 1944. There is also a number 2, which could be February, even though the unreadable ideogram on its left does not look like being the word "month".

The fourth row finally proves that it was made by Asahi Optical Co., as it contains the full official Japanese name of the company: "Asahi Kogaku Kogyo Goshi Kaisha".

The case
When opened, the case exposes a nice custom made wooden interior that is entirely hand finished. The lid is leather padded to ensure that the contents of the case are firmly seated. The contents of the case are rather strange and consists of two separate items. First something that looks like a black painted pipe with a triangular shaped item on one end, and a female screw thread on the other. And just above the female screw thread there is what appears to be a binocular eyepiece. The other item is a wooden stick that looks as if it might have come from a black lacquered wooden stool or another piece of furniture. The stick ends in a male screw thread and it screws into the pipe. The resulting item looks rather odd, but with the information provided by the seller and the information on the label it made perfectly sense, because this item is what is essentially called a "Trench Periscope".

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Trench periscope
A periscope is an optical device for conducting observations from a concealed or protected position. In its simplest form, a trench periscope consists of reflecting mirrors and/or prisms at opposite ends of a tube container. The reflecting surfaces of the mirrors are parallel to each other and at a 45° angle to the axis of the tube. As its name implies, a trench periscope could have been used in trenches to spot enemies without risking your head. After some research, I came to the conclusion that not everything was right with this item. Many military items are usually painted green and that is why the case has a olive-green color. But I cannot imagine going into a trench and then spotting my enemies with a black periscope. It would be like wearing a white suit in a crowd of women wearing black dresses. So why was the periscope not painted green? We can only guess, but everything has its meaning. It’s quite possible that the periscope was not meant to be used in trenches at all. An indication abouts its use can be found in the Hong Kong Museum of Coastal Defense because the same item is on display there. Was it used from inside a dark bunker to watch the sea?

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The trench periscope in detail
The pipe, including the triangular shaped item (which is in fact the upper mirror in a metal casing) is 44cms long. The wooden handle is 24cms long. So, when completely screwed together, the item is 68cms long. The upper mirror is mounted on a sliding iron rod so that the length can be extended to a total of 83cms. The triangular metal casing of the upper mirror is also important because it features the well-known prism-shaped AOCo logo. This proves, without doubt, that this logo was already in use during wartime. The logo probably even dates back to 1938, although that would be hard to prove.

The "5 x 10°" marking above the logo shows that the trench periscope has a 5x magnification factor with a field of 10 degrees (at 1000 yards or meters?). Below the logo, the serial number 8411 is engraved. This matches the serial number on the case. Finally, below the serial number, there is a very small box that encloses a difficult to reproduce Japanese ideogram. It is the same unknown ideogram as on the metal label.

The eyepiece is adjustable from +5 to –5 and it is the only way to focus the image. When looking through it, a scale can be seen. This scale, which consists of vertical lines, has a zero mark in the middle and stretches out to a value of 50 on both ends. This scale is probably used to determine the size of subjects at the horizon.

The glass elements and flat glass surfaces used in the trench periscope appear to be uncoated. It is common knowledge that Japanese and German manufacturers applied a simple coating to lenses in WWII. However, it is too easy to state that all military optical items had coated lenses. It probably was not that common at all and only used on the most expensive optical items (for instance the giant ship binoculars made by Nippon Kogaku).

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It’s great to finally come across an AOCo-item that definitely dates back to WWII. Asahi Optical Co. probably was not a large manufacturer, but this item shows that, during wartime, the company was indeed producing interesting optical items for military purposes. This also adds to our knowledge of the company and its history.

It would be nice to find more items that date back to WWII or even earlier. There’s definitely more to be found. If you know about such items, then please share the information with us!

This article could not have been as informative as it is now without the translation of the metal label by Miss Megumi Yugeta.

The original article was published on SPOTMATIC magazine #35, January 2003.

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