The mortar is a early 4" bronze mortar, that were often fitted to a simple plank of wood - Oak 20" long, 10" wide x 4" deep. The tube was set at a 45 degree angle, and the range altered by changing the amount of propellant charge. Sometimes they simply changed the angle of the wood base, to change the range a short distance. Baron Menno van Coehorn (Dutch) designed and built the first wrought iron ones, used at the Siege of Grave (1674). The first English bronze ones were in the Tower inventories (London) by 1713. This one came off a 1718 wreck, an early model to say the least.
Jim J.