The Hunter Arms Company was formed when John Hunter Sr. purchased L.C. Smith Maker, from Lyman Cornelius Smith in 1888 in Syracuse, N.Y. The machinery was moved to Fulton N.Y and production was then began around 1890.
The Hunter Arms Co. was run by John's six sons. Many of the early Fulton L.C. Smiths had the same attributes as the Syracuse L.C.Smiths, the sqared barrel lug, the convex ribs on the under side of the receiver, 24 lines per inch checkering on the lowest grade Quality 2's, good Damascus barrels, large breech balls and the joint check ejector system. Many of these Syracuse changes were slowly phased out, manly because of man hours/cost.
The highest grade Fulton gun in a calalog of 1892 was the A2 with automatic ejectors, Finest Damascus steel, finest imported English walnut, finist checkering and engraving. The price then was $390, and it was made in 4 different variations of engraving, and the first one has stepped lock plates reminisant of the Syracuse Quality 6 and 7 grades.
The lowest priced gun then was the Quality 1, Stub Twist barrels, line engraved Enlish walnut, price on application ($60)
In 1895, the A3 was made, it was described as the finest shotgun made in the world and it's price then was $740, the most expensive shotgun made here or abroad. The barrels were Sir Joseph Whitworth fluid compressed steel, the engraving was your choice, finest figured Circassian walnut, 32 lines per inch checkering, and as many coats of oil to finish it. There were only 18 made, 16 in 12 ga. and 2 in 20 ga.
I could go on, but the best way to learn about these guns is to buy either Col. William S. Brophy's book "L.C. Smith Shotguns" or for more details and pictures, John Houchins book "The Legend Lives, still available through the Double Gun Shop.
Your son's gun is built on a Regular frame, starting in 1907 they were also available on a Featherweight frame. Most Featherweights were lighter than a Regular frame, but not all.
The Field grade before 1912 was a 00 grade and was the lowest priced hammerless gun made. Then it cost about $32.50 net, but you could order it with automatic ejectors for $10.00 more and the Hunter One Trigger for another $10.00. There were 195,205 Field Grades made.