The arsenal mark is as close as I could get to what remains of that mark on the primer. It was much fainter than the others.
Here’s my rendition of the headstamp marks. The last in the line of marks was very faint and appears to be double-struck, but not certain.
Any idea what the stencil markings on the side of the case say(mean)?
As for what your case reads:
I can only be certain of the two rightmost characters. This text should be read from right to left. The rightmost character is the Kanji for the number ‘9’ and the second character from the right is the Kanji for the number ‘2’, hence, together forming ‘92’, the type (or rather, ‘model’, when translating it more purely) designator. If you can post a somewhat clearer picture of the two (?) leftmost characters, I can look them up for you. From the top of my head, I think they would indicate the type of load or usage, but I’ll have to check.
Headstamp (in clockwise direction):
1-‘F’: As far as I know, this indicates ‘Army’ usage.
2-‘1’: No idea.
3-1 Kanji character, drawn by you as if they were two characters: the short notation for ‘Showa era’; the base year for calculating the date.
4-’+’: Kanji for ‘10’
5-’/’: Kanji for ‘8’, together with nr.4, this forms Showa year 18, being 1925 + 18 = 1943.
6-‘5’: Month of manufacture, Western notation; in this case: May.
7-Arsenal mark: I’m not certain which arsenal this is. The suggestion of Mukden is at variance with other arsenal marks I have seen listed for that arsenal. I’d love to find out for sure!
8-Kanji/Hiragana character: typically, a short notation for the city the arsenal resides in.
Primer (in clockwise direction - starting at 1 o’clock position):
1-1 Kanji character, the short notation for ‘Showa era’; the base year for calculating the date (Note: this is the same character as nr. 3 on the headstamp).
2-’+’: Kanji for '10’
3-‘t’: Kanji for ‘7’, together with nr.2, this forms Showa year 17, being 1925 + 17 = 1942.
4-‘4’: Month of manufacture, Western notation; in this case: April.
5-Arsenal mark: again, not certain which one… definitely the same as the case manufacturer (which is not always so on Japanese cases, which often are Osaka made, with Tokyo primers).
6-Kanji/Hiragana/Katakana character: possibly, a short notation for the city the arsenal resides in, or some short notation for the usage, or material?!? Not certain…
NOTE: Hiragana is rare or none existent on Japanese ammo, as it wasn’t really used for designations back then. Yet, Hiragana is the more ‘curly’ style of Japanese characters, so I can’t rule them out from the mere drawings… Most likely they are Kanji, as they seem to be too complex to be Katakana. Also, if the case was really made at Mukden arsenal, there is also a chance that these characters are actually Chinese, rather than Japanese. I’d be very interested to see this answered for sure by someone who’s knowledgeable in these Asian scripts…
I just searched somewhat in Wikipedia, and check out this link: http://en.wikipedia.org/wiki/Mukden, take particular notice of the first of two Asian characters in the 3rd line in the main article, starting with the text: "Shenyang (Ch.: 沈阳; pinyin: Shěny