This headstamp appears on three used empty 12.7x76 (.50 Spotter) cases that sold in auction today.
The vendor’s description (translated from Japanese) says the headstamp means Made in Japan - Nippon Koki Co., Ltd., Shirakawa Factory, Weapons Department. Made in 1978.
Cropped and enlarged photo from the auction;
I found this brief note relating to their R&D Dept online here, nof.co.jp/english/business/r … realm.html
Nippon Koki Co., Ltd., Shirakawa Plant, R&D Department
This site is primarily focused on R&D pertaining to defense-related equipment. However, leveraging its high-precision technologies and expertise accumulated over many years, the Shirakawa Plant is also carrying out the development of new products in fields such as industrial explosives and industrial high-precision products, as it seeks to meet the needs of customers in a wide range of industries.
Ron Fuch’s 50 cal book mentions J-N S W 0 5 on 12.7x99 (.50 BMG) cases.
Does anyone have any information to add?