Those numbers above look like stamps from a modern # set. I wondered about the smaller marks too.
No Grade marking on the bbl set? or is that tiny Df in the upper left corner perhaps some sort of a grade marking.
In looking over the set of pics and using the Zoom image function in the upper right corner.,
I see a lot of checkering over runs on the 16ga wood both butt stock and forend.
The pointed tail of the trigger guard does not seat in it's inlet in the stock,,nor does it really match the inlet.
The trigger guard screw is buggered up (as are the trigger plate and butt plate screws).
The trigger guard tang has a couple flat strikes on it as if to straighten the curve out. No signs of a recut.
The trigger guard looks like it should screw into the trigger plate one more turn to tighten up all the way.
There are chips in the butt plate countersink edges around the screw holes. Small, but they are there. I wouldn't expect them there if the gun hadn't been taken apart a few times with an overly wide bladed screw driver. No engraving on the screw heads has been pointed out.
The 20ga bbls have had their roll stamped lettering on the top of the tubes enhanced (hand recut) especially at the beginning of each line. The first few letters of each line needed to be recut but you can sometimes see the orig letter underneath or beside it. Not the best of recut jobs for sure.
The 16ga bbl have been polished & reblued. Buffed lettering and engraving.
The triggers were gold plated,,probably originally. What's left is on the protected areas and has some old dried oil and dirt on it. The trigger pads themselves are worn off completely to bare steel.
The rest of the gun is near 100% despite the handling that wore the triggers to bare steel. I realize gold wears easily, but no wear at all on the rest of the gun?
...and that top lever way to the right...it was bent to the right.
The thumb piece stem itself is bent over to the right to make the lever and the gun appear to be in super tight lock up condition.
Draw a line straight down the center of the top lever and you can easily see the bend.
An old trick, but this one over done.
When the lever bolts up in the center or even slightly to the left,,,bend the thumb piece to the right slightly and presto,,you have a top lever to the right.
You need to anneal the top lever to do this generally, so I suspect it was done when the parts were annealed for re-CCH.
The frame, and parts look re CCH to me. All very new looking with no wear (those worn triggers again).
I also suspect the 16ga wood to be refinished or in the least recoated with finish to brighten it up some. Probably a French Polish overcoating to enhance it.
A factory letter?,,all that will tell you is that 'A' gun left the factory w/a certain ser# and features. It doesn't ever imply that the one you have in your hands is THAT one.