'Flues' Model,,
Grade 1 1/2.,,
Should be some serial number tables on the net for the Flues. 1908/09 till the mid 20's when the NID took over in production.
RST is where most buy their low pressure and odd length shotshells
Classic Shotshell Co. Inc., RST
The old Flues in 20 ga probably has 2 1/2" chambers if they're still original.
I don't recall when they started chambering 2 3/4 as standard in 20ga.
Some of the 20 and 16ga Flues were built to very light weight specs and have come up with cracked frames at the corner of the table and standing breech.
The very thin recoil shields on the guns is usually a hint that it's one of the lightweights. The bbls are filed out thinner than normal too.
Hard to tell in the pics,,I've seen them thinner than that on some guns. They were hand filed to get the weight down so they vary some.
It's not the guns fault for the failure,,just the owners fault for putting loads through it that were never intended for the gun. What was Nitro Proof than is not Nitro Proof today.
Purists cringe at the thought of lengthening the short chambered Flues especially the light weight guns as the bbls are thin to start with.
But check it over, threat it right and it'll be around for a long, long time.
Heavy loads will just cause the stock to crack at the top of the 'ears' anyway.
Keep the top tang screw tight. It's only a short stubby wood screw, not an interlocking bolt with the trigger plate. So it doesn't help nearly as much in securing the wood to the metal as other designs.