Midway: Primary Distinguishing Characteristics
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The primary identifiable features in the piece of wreckage are the two gun tubs, the gallery structure attached to either side of them, and the landing light array attached to one of the gun tubs. In order to identify the ship, we need to positively identify these items.

Gun Tubs

Japanese warships were notable for the variety of projecting platforms that typically festooned their sides and superstructure. These platforms were used to mount a wide variety of equipment, including spotting glasses, fire-control directors, radio aerials, and guns. However, the sheer size of the wreckage platforms (approximately 14 feet in diameter) rules out Type 95 directors and minor equipment such as spotting glasses. Furthermore, a 14-foot wide tub is too small to be a platform for either a dual 120mm or 127mm gun mount. Heavy AA guns of this type were typically mounted on individual platforms which were around 21 feet in diameter, and were supported by much heavier central support columns. However, 14 feet closely matches the size of dual 25mm anti-aircraft gun mounts (as taken from scale drawings of Japanese warships of the period). Furthermore, the fact that these tubs were part of a gallery structure (i.e. a grouping of gun tubs connected by walkways) indicates that the tubs were for 25mm mounts, since heavier weapons tended not be part of a contiguous gallery structure, but were sponsoned out individually from the ship. For all of these reasons, the evidence strongly indicates that the wreckage platforms are dual 25mm gun tubs.

Bulkhead Structure

Despite the top-down (or more accurately, bottom-up) nature of the underwater photographs of the wreckage, some basic characteristics of the bulkhead to which the platforms are attached can be made out:
1.   The bulkhead is from a relatively flat-sided portion of the ship.

2.   While the gallery structure between the gun tubs has been largely crushed by the distortion of the object, there do not appear to have been any major structures in this area.

3.   From undersea video footage shot of the object, a porthole can clearly be seen. This porthole is not visible in the top-down photo mosaics, but is to be found on the extreme right-hand portion of the bulkhead structure, approximately five feet away from the support structure of the right-hand gun tub.

Figure 11: Landing light array, with red lines denoting major structural members. Note asymmetric shape. Dotted lines indicate probable position of three missing landing lights. The wires at the end were rigged fore and aft and were used to stow the array.
Landing Light Arrays

The wreckage attached to the left-hand gun tub closely matches a Japanese landing light array, despite having been crumpled by its impact with the seabed. Identification features include:
1.   The structure is roughly a right triangle in shape, which indicates that it is not the lower portion of a radio aerial. Aerials were more symmetric in nature, and can be thought of as being a very long, skinny pyramid.

2.   Radio aerials appear to have been composed of lighter gauge steel (which makes sense for a rather long object that must be able to be lowered in and out of a horizontal position by a relatively small motor). By way of contrast, the main bar of the wreckage on the bottom is rather heavy looking. The fact that this bar also has holes drilled in it indicates that this particular protrusion needed substantial structural strength (and hence was composed of heavy gauge steel), but that the builders were also concerned with the overall weight of the structure. This usage of perforations in main weight-bearing members to reduce topweight is typical of Japanese naval construction.
3.   Radio aerials were much larger (30-40 feet in length) than the 12-14 foot long object attached to the gun tub. The object appears to be unbroken, and ends cleanly at its terminus (except for trailing wires). A radio aerial, since it is composed of several long structural members, would be expected to break less cleanly in the midpoint of its length if it had been torn in half here.

4.   The presence of the white rectangular object on the upper part of the arm closely matches the size and shape of one of the landing lights. The positions of the other three lights are indicated on the annotated diagram of this piece of wreckage.
In summary, this piece of wreckage is a landing light array, and not a radio aerial or some other type of antennae.
Primary Identification Characteristics

The remainder of the ship identification process centers around finding a ship that matches the wreckage. This means finding a portion of a ship that meets all six of the following criteria:
1.   A large portion of a 25 mm machine gun gallery,

2.   Attached to a flat portion of the ship,

3.   With a porthole located about five feet from one of the gun platform support struts.
4.   Where two of the 25mm tubs are adjacent to each other, without intervening fire-control equipment or other platforms between them,

5.   And where the gallery structure continues on either side of the tubs for at least 7-8 feet in each direction,

6.   And where one of the gun tubs has a landing light array attached to the outermost point of the tub.
From these six requirements, a positive identification of the ship can be reached.

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