Can anyone date this box of .303?

Head stamp is UMC Rem 303 Brit. No date

Here is a white box of M193 Ball that was available on the secondary market in the late 1960s. most of the boxes had the lot number removed. The head stamp is RA 67.

Odd, that.

"Mil Contract" ammo tends to be a little more cryptic in the headstamp department, usually NOT showing cartridge designation, for instance.

The 150gn bullet thing is another thing. What "proper" military ordnance system would purchase "odd" ammo for general distribution. By "odd" I mean ammo that has a completely different trajectory and ballistic performance from that around which EVERY weapon in that caliber in the inventory was built.