I got the idea for this flag from an article in Wargames Illustrated, (sorry I can't remember which one), although they do point out that some sources say they carried plain black standards, I think it looks a little more colourful having the crown and monogram. I've included the regimental standard which may have been carried by the first company with the others carrying guidons.
The Regiment Garde Dragonders, to give them their full and proper name were raised in 1672. It was in English pay between 1 January 1689 and 11 October 1698. During the Nine Years War, the colonel of the regiment was William III, Prince of Orange, but he was somewhat busy during the period to command them on the field, so that honour went to Colonel-Commandant Abraham van Eppinger.