Hi guys,
Dow already knows this (as he asked me by e-mail) but for those of you who haven't seen this, you may want to check the following section on my site:
http://www.japaneseammunition.com/start.php?main_cat=14&sub_cat=176
Scroll down to the bottom of the page for links with detailed descriptions of the specimens of my collection (particularly the very last link, with the headstamps pictures is of interest).
Yes, Dow's headstamp is strange; the strong concentric circles are somewhat odd, but even stranger is the "half" set of markings: i.e. not completely headstampless, nor provided with a full headstamp. His casing is identical to one that I own, as well as one that I know Kornel owns. Those are the only three I've seen with this very headstamp (though I think that the seller of these casings over here has at least one more). The casing was made at the Toyokawa arsenal, but no manufacturing date seems to be present on it. The 'o' or '0' is wildly odd.
Japanese 25x163 casings seem to have come with headstamps until late 1943, after which they came headstampless. The latest one I have with full headstamp is a Dainippon one, from June 1943 (I have a lot more incoming, so I may soon have later specimens). Possibly this reduced set of markings was used as of mid-1943 to late 1943 (Ken Elks mentions something about a reduced headstamp style in his books - I'll check that later).
Now... maybe unnoticed by all, but the REALLY weird thing shown in Dow's pictures are the markings on the projectile! I've never seen that! I'm trying to figure out what the story is behind those, as I do not recall any mention of that in my reference material.
To be continued...
Cheers,
Olafo
PS: Kornel: headstampless casings are not so uncommon; apparently as of late 1943 all of them came like that.