We in Britain also stamped our bullets with a manufacturers code, 'though not as elaborate as that of the French. UK .303" bullets had a stamp into the lead which served two purposes, it identified the origin of the bullet and it indicated to the inspector that the bullet was correctly pressed. If insufficient pressure had been applied to the base the mark would not be clear, this could indicate a machine fault or a missing tip filler so the bullet was rejected.
Other bullets, such as .455 Webley and .380 revolver had base marks too. The inside of .303" cases also have marks at the bottom to indicate the maker of the case (which is not always the same as the headstamp).