One of the only two known authentic Jolly Roger pirate flags in the world.
Prior to the advent and popularization of the "Jolly Roger" we know today, western pirates flew a simple black flag, initially devoid of design.
The black flag was part of a flag signal combo, together with a plain red flag. After closing in on a target ship, the black flag would be raised, signaling that "quarter" will be given if the target crew surrendered their cargo/valuables without a fight. Followed by warning shots, if the enemy did not strike their own flag to signal surrender, the red flag (or bloody flag as it is known) was raised, signaling that the target’s cargo/valuables will be taken by force and that "no quarter" will be given if the enemy ship continued to refuse surrender.
The pirate captain Jean Thomas Dulaien would wait for the enemy to fire three or more cannon shots after raising the red flag before giving the order to attack with no quarter given.