Assistance with identifying A6M Zero Inspection Stamps

[Markeight]

Hi all, first time poster so go easy....

I've been seeking answers to this question around the 'net but to no avail; I am wondering if anyone on this forum knows anything about inspection stamps on components of Japanese aircraft from World War Two, as I am having trouble confirming some information I have seen in other locations on the web.

I identified sections of an A6M Zero during recent travels through the Pacific, while examining a few of the pieces I came across inspection stamps on some fragments of the aircraft from the internal wing structure. I can identify the Mitsubishi logo, what appear to be part numbers, the SDCH acronym and - the ones I can't figure - the number 17 in a small circle, and a small Kanji character marked on the pieces that I can't ID (see images).

The only references I've seen on the internet to the number in the circle is that it means 'Showa 17', that is, it was made in 1942 - can anyone positively confirm or deny this?

Apologies if this information has been discussed elsewhere; any assistance greatly appreciated!

 

[Shinpachi]

Welcome to the forum, Maticash.

The aviation material rules of IJA/IJN which was published in 1939 instructs makers
1. to put a seal which shows the aluminum type and
2. to print the heat treatment type like "SDCH" with no-corrosive ink on the surface of aluminum products.
Need scrutiny but, to compare the rule with modern JIS (Japan Industrial Standards), your first "17" seems equivalent to JIS 2017.
Your second pic looks like "下" which means "down".

 

[Markeight]

Hi Shinpachi, thanks for your welcome and the information.

The JIS information sounds like it might be right to me, I've had a look around the web for other information on Japanese inspection stamps and have only come across images of a few examples, but most I've seen have been of the 17 in a circle - the only other I came across (which I cant remember where unfortunately) was of a 24 in a circle, which would fit in with what you've provided here. If the Showa 17/1942 theory was true (which I always doubted) then that would have had the '24' example being constructed in 1949 - clearly impossible. I thought it may have been an inspectors identifier also, but the fact that there was usually only the number 17 represented made this rather unlikely (either that or there was one particularly busy inspector at Mitsubishi!!). As you said this may require further scrutiny, but at the moment it seems the most plausible explanation.

The meaning of the 下 character is interesting; it is marked on two separate components in the piece I examined which, based on other wrecks I've visited, I think comes from a wing near where the landing gear strut sat when raised (see attached picture). Unfortunately the wreckage was very badly mangled so I could not confirm this - perhaps you might be able to confirm this? (sorry for the poor quality image!)

f

 

[Shinpachi]

No exact idea but, frankly, looks like an overhang on the flap of a bomber like the G4M.
Just my impression.

 

[Markeight]

Nope, definitely a Zeke, here's some of the other bits of it Can't figure out what model it is, pretty broken up and my ID skills aren't that good - any suggestions greatly appreciated!!

External starboard side of fuselage with wing root

Internal starboard side wall of cockpit with undercarriage wheel well

Internal panel from port side of cockpit with scale

 

[Shinpachi]

Looks like an A6M2 as no traces of green color on the outer skin but light grey.
Nice pics