Granate ???

[kz11gr]

Hallo,
Jemand kennt ?
verkauft auf ebay / WWII SHELL CASING
Ebay Item # 729395563

[kz11gr]

text : Up for auction is this brass shell casing. Can't find any markings to help me identify it. If you know , let me know. The widow I acquired it from said her husband was assigned to a B-29 during WWII. It measures 4 1/2" long by an inch wide. The 8 barbed spikes that open are app. 2 1/2" long. As you can see by photo the barbs stay closed with an allen wrench, once you remove that it pops open.

[megatron]

Ouch....

Looks a bit like for an anti balloon gun or so. But doesn't make too much sense...
Probably the tip of a harpoon?
Can you figure out the correct diameter?

[kz11gr]

For the diameter , the only information is given by the seller :
It measures 4 1/2" long by an inch wide. (25,4 mm)
This item is still on ebay , but sold .