This is a self-made speaker grill kit. The previous owner apparently bought it for the Nagaoka enclosure D-55. The manufacturer and details are unknown. Attach it to the enclosure using a pin method or adhesive. The appearance is good with little feeling of use (Kobayashi Hitoshi)
Accessories: adhesive, fixing pins, installation instructions
Main specifications: Iron net polyethylene coating frame is acrylic resin painted on plastic, diameter 185 mm