Depicted in the photos is a cartridge being advertised as an explosive round. As you can see it has 303k on the headstamp. From my reading it seems k could refer to one of the first two incendiary rounds which were actually explosive per Tony E and were dealt with as such on his website.
The bullet looks like the VIIK Mark I in that the hole in the nose is 0.09" in diameter as Tony says. However it does not have the priming charge that inserts in the hole.
Please let me know what you think this is and thank you.