Help ID WW2 Navy Shell

Hi All: New member seeking help to ID Grandpa’s WW2 memorabilia. All we know is he was in the Navy fighting in the Pacific theater. I’ve uploaded pictures of a shell we are trying to ID. The shell is wrapped in a paper tape like material. Any help is much appreciated. Dave

May we see the bottom? There may be something written there.

Japanese 20mm Type 99

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Brian, what is the “thingy” on the nose fuse? Looks like some kind of a locking mechanism. And do you think it is the middle one “high explosive tracer - self destroying”?


I’m away from my library so cannot properly answer your questions :-(


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During WW2 solders were allowed to bring back “souvenir” pieces such as this BUT such items were supposed to be deactivated and inspected by trained personnel.

I suspect (but cannot confirm) the reason for the brown packing tape is to keep the projectile and the cartridge case together since it was standard practice to pull the projectile from the case and dump the powder. As a result of doing this the projectile no longer fit tightly in the cartridge case.
Like wise the brass fuze in the projectile nose appears(?) to have been unscrewed, note the plier marks in the brass and the fuze does not appear to be tightly screwed into the projectile. This may indicate (but cannot confirm) the contents of the projectile have been removed during deactivation of the cartridge.

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You read my mind about brown tape.

Thanks Brian / Vlad: I suspected it could be a Japanese Souvenir. I’ve included some more pictures as well since the system only allows me 1 upload. How can I verify deactivation? Would weighing it provide an indication if a spec is available for comparison?

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Another picture.

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the case is inert as it has no primer.
The fuze is poorly fitted and may or may not have been inerted.
The paper covering may also be covering a case hole near the case mouth.

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I suggest you change your title of this thread to something like

“Help needed with Japanese WW2 20mm round”

Hopefully that will get the attention of people who know a great deal more about Japanese items.


All great info … the wealth of knowledge is more than I had expected. Thanks everybody. Post title changed as suggested and one more picture.

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CinCPac-CinCPOA Bulletin 157-45 “SOUVENIRS” was written sometime after the surrender of Germany, but before the defeat of Japan, with the following guidance on souvenirs. There were likely other similar documents, or changes to this document, issued after VJ-Day as the quantity of Japanese ammunition souvenirs is much larger than might have been smuggled home in violation of the directions here.

(pages 11-13) "It is an offense, punishable by court martial, for unauthorized personnel unnecessarily to handle or attempt to disarm captured ammunitions. Trained personnel are present on each operation to handle enemy munitions as necessary.
The retention as souvenirs of explosives and ammunition, or any part of component thereof, is expressly forbidden. The ‘any part or component thereof’ means that you are just wasting your time if you try to turn a shell into a fancy ash tray, lamp, picture frame or letter opener. The articles are parts of shells and will not be allowed as souvenirs.

It’s very easy to say, ‘I’m sure the shell I am sending home is completely safe’, but there have been too many cases of ‘safe’ shells reaching the states and killing people…"

The complete document can be downloaded from:

The above talks about captured ammunition. Was there a similar directive about American or Allied ammunition (to be brought back to US)?

Thanks JohnS. The souvenir policy makes all the sense in the world, and the potential danger is why we handle this with extreme care. So the obvious question…what do we do with this thing now?

As I noted, there were probably changes or different instruction s issued at later dates. I suspect some of those may have allowed ammunition items which were declared safe by EOD (or something like that). We see an awful lot of Japanese 20-25-37mm ammunition and knee mortar rounds which have been deactivated. I suspect this was done during the occupation of Japan, not during the war itself.

As for the initial item above, my opinion, not having examined it in person, is that having the primer removed strongly suggests it has been rendered inert. It looks like the fuze has been disturbed from its original position and any waterproofing applied has been broken there. If the fuze can be unscrewed with your fingers, you can look inside and see what is there, but don’t mess with pliers or anything. If it cannot be unscrewed then the old Dirty Harry line applies “Do you feel lucky?”

Whatever the rules, sometimes they are not followed, and some live Japanese ordnance items did get sent/brought home and can be found today. Let the professionals have their fun with them, if at all suspicious about their safety.

If you call local authorities, they will come, probably with police, fire, news media, etc and evacuate the neighbors. It would be best that the item is outside so they don’t have to prowl around in your house. Ignore the news media (don’t answer the door or phone, not a single word!) who will hound you for comments while they speculate about how many blocks will be destroyed if the thing blows up, and what sort of twisted person would have a deadly weapon of war in their peaceful city, etc. Better safe, and harassed a bit, than cope with an explosion, which would get even more police and news attention.

Another approach is to bring it to an AMMUNITION show (not GUN show) depending where you live.