US Navy Ithaca Model 37 "Duck Billed shotgun"

Does anyone know what these are? I cannot find reference to it. I spoke to a Navy Vietnam Vet about some strange shotgun ammo that I found in Hawaii. It had been a wonderful and insightful visit as he shared stories and some photos of himself where he commanded a NAVY PBR on the Delta Mekong River. It was his job to stop and search vessels on the river as well as accompany Marines and Army personnel up the river. He examined the can and the packages of ammo. He stated that aside from the OO Buck he was issued. He alo recieved some of this ammo for use his Ithaca model 37 "Duck Billed shotgun"...??? Any photos out there? Ideas?

The markings on the can are as follows:

120 CARTRIDGES
12 GAGE, SHOTGUN
PLASTIC
NO. 9 CHILLED SHOT
2 3/4 DRAM
LOT WCC-30-6002

The markings on the packages are as follows:

10 CARTRIDGES, 12 GAGE
SHOTGUN PLASTIC CASE
NO. 9 CHILLED SHOT
2 3/4 DRAM
LOT WCC 30-6002
OLIN CORPORATION
(VCI PACKAGED AND DATED 3-72)

Thanks in advance!:sos:

The Duckbill Diverter is a choke device that creates a more open eliptical shot pattern. It was sparingly used during the Vietnam War. There's a photo of one in Bruce Canfield's US Military shotgun book.