Here is a FW Rochester Ordnance Smith (ROS) with the markings:

FJA - Ordnance Flaming Bomb - Ordnance Crossed Cannons

So what we have so far is:

Field Grade WILD FOWL marked Shotguns

1. RLB - Ordnance Flaming Bomb - Ordnance Crossed Cannons
2. FJA - Ordnance Flaming Bomb - Ordnance Crossed Cannons
3. Ordnance Flaming Bomb
4. (Possible Armory Markings) - ILL or VA followed by numbers

Field Grade Featherweight

1A. RLB - Ordnance Flaming Bomb - Ordnance Crossed Cannons (See photo Ser # FWE 198805)
2B. Ordnance Flaming Bomb
3B. FJA - Ordnance Flaming Bomb - Ordnance Crossed Cannons (See photo Ser# FW 199979)