Quite rare and interesting family of japanese army commemorative watch fobs. Basic info about Nomonhan Incident https://en.wikipedia.org/wiki/Battles_of_Khalkhin_Gol...
Size 57x53.5 mm. Weight 30.6 g. Obverse 偵 - Reconnaissance reverse 2600 = 1940 卒業記念 - Graduation Commemorative 操縦第八十二期 - 82nd Class of Pilots [flying a plane] 宇都宮陸飛行学校 - Utsunomiya Army Flight School Engraved 大善 - Daizen (name) Original case. 卒業記念 - Graduation Commemorative