Yes the founder was Jan Verbruggen as someone guessed. The last part of "Verbruggen" is corroded off, but there's no question as to what it is. This was cast by Jan probably around 1750 when he was still in the Netherlands before he went to England. He cast this for the Dutch East India Co., if I didn't mention that before. They had these at their forts in Batavia. If anyone is new to stone mortars, they used pre-prepared special wicker baskets filled with either round, probably baseball-sized stones, or grenades. The grenades were supposed to have their fuzes lit by the propellant charge. The stones or grenades would come down on the heads of the enemy troops who were trying to enter the fort and make it unpleasant for them.
Thanks for the suggestions, am working on a few options of either shipping to US or leaving in UK under circumstances favorable to Springfield Arsenal LLC. There was a 42 pounder bronze carronade and a very old 10" mortar in the same group, that we didn't buy.