Keberst .338/.416 Rigby

I have a cartridge I have had for about 20 years that I need more information on. At the time I got the cartridge I wrote “Keberst .338/.416 Rigby” on it, but I no longer remember anything about this round. It has a GM pointed FMJ bullet and a very flat head without any headstamp.

Does anyone have any details about this round? Who is Keberst? Is this the same round as the .416/.338 U.S. NAVY-HASKINS SNIPER?

Ron -
Let me try one more time to reply to your questions -
There is a good explanation of the history of this cartridge and Keberst on the Lapua website - - under ‘special purpose the story of the Lapua Magnum’.