I am very interested in your project and apologize that you have not received a better response from the Park Service
Seems to me I saw the companion piece to this mortar on sale on-line not too long ago? I cannot find it now.
Anyway do you have photos of that piece and/or know who has possession of it? The folks at the Florida Museum of History were interested in hearing about it and may be of some help in this. I would also suggest talking to Charles Tingley at the St. Augustine Historical Society.
It's not that the NPS is indiferent, this is indeed a spectacular piece as are most of the bronze pieces in the Castillo inventory, there are just so few resources available to us, and even less time, to do these and the other artifacts we hold justice. I will look into what few records remain here in our library on the British Garrison ordnance, most were moved some years ago up to Fort Caroline.
The Spanish as far as I know took their all their ordnance with them in 1764 when evacuating Florida, as did the British in 1784-5, this was typical for treaties of the day (Which points to some hubris on the Americans part in not conceeding to this) These mortars would have been part of the resupply during the second Spanish period.
Anyway, I will help in whatever way I can and hope that you will be willing to share what you find with me.
Historic Weapons Supervisor
Castillo de San Marcos, NM
To Join the Company of Military Historians click here