WW2 rounds - some familiar but one thick heavy bullet that's hard to work out

Hello, I’m new to the forum. I’m in Australia and I have come across a bunch of rounds, some of which I have info on others not. I’d appreciate any information and if there is any value for resale. They’re marked: K2 20mm 1942 (and 253/1 M on tip), RA 42, DM 43, but there’s one I can’t work out - vague markings - big bullet head (around 3 inches long by an inch thick) head marked 1063 and on side C then P or D, possibly K or faded slight smaller word, then either O or backward C with a small E next to it. I am also wondering what their value might have. Any help is appreciated. Cheers

First bunch are .50cal (12.7mm x 99mm)),RA and DM are US headstamps.

The 2 in the middle are British 20mm Hispano (20mm x 110mm), first is a Ball round, second is HE/I(High Explosive/ Incendiary).

The larger projectile looks to be a 2pr or 40mm Bofors AP/T(Armour Piercing /Tracer). Though without detailed measurements, could also be 37mm…any number of nations.

Hi Takapu, thanks very much for the info. Do you know if people collect these - is there any value to them? Cheers

Here’s is an image with the potential Bofors height

@Takapu Here are other markings and size

@Takapu Here are other markings and size

The large black steel projectile is a 2pounder Armour Piercing projectile for the 2 pdr anti tank gun.
The others are as previously mentioned, 20mm Hispano aircraft canon, both being High Explosive style with brass fuze on the end of the projectiles. 1 is painted in its original colour scheme. & .50cal Browning Machine gun rounds.
Regards Ozzi.

Thanks for the additional clarity @ozziammo
Cheers