I picked this one up recently. I’ve been trying to make sense of the label inside with some success after referring to the posts here and Nick’s guide on WAF. But I still don’t understand a few parts of it. First, photos:

Here’s what I’ve got so far.
入籍番号Entry Registry Number 舞一補三九三六 Maizuru 1st Reserve 3936 (overlooked on the label and added off to the side on inside of cap) 水 (水兵) sailor
Nick’s article mentions that officers should have a 5 digit number. As the owner was called up from reserve perhaps he started off in the enlisted ranks.
氏名 Name 大谷 春吉　Otani Haruyoshi
交付年月　issued year month 十八年　十二月　(Showa) 18 year 12 month (1943 Dec.)
寸法夂 Size ? (not sure what 夂 adds to 寸法)
裂作年月 ?? year month (don’t understand 裂作)（一）十七年 九月 (1) 17 year 9 month (1942 Sep.)
舞鶴軍需部 Maizuru Depot

Click to enlarge the picture