Dean is correct. The crossed flags, all by them selves with no extra crowns, letter or other embellishments are acceptance stamps, not proof marks. British & Colonial ordnance manuals list the various proof marks and the codes for identifying the arsenals or proof houses that applied the proof mark. There is no listing in the manuals for crossed pennants (or flags) by themselves as being a symbol of a proof. There are numerous variations of crossed pennants & flags with the additional crowns, letters, numbers, symbols, etc. of the proof activity, however the naked crossed pennants are not proof marks but are acceptance stamps. Ed.