This is a smaller and exposed rangefinder used to measure target range for smaller guns such as the 25 mm anti-aircraft guns. This particular example is located amidship on the Akizuki class destroyer. I am afraid details are low since I could only find a single diagram for this instrument on the Grand Prix book on carriers (page 281). I would be happy to upgrade this image if I can get a more detailed drawing from my readers. In addition, I am also concern as to whether this is actually the right instrument on this ship. The Grand Prix book on destroyer identified this as the correct size director (page 238). However, the Maru Special (Mechanism of Japanese Destroyers & Torpedo Boats, page 99) identifies it as a 2 meter rangefinder. This could be due to a difference in the stage of modernization of these ships. I would be delighted to hear from readers with better reference information than I have.