The gun was orig made/proofed in March of 1923. (3.23 marking on the bottom)
The 24 in a circle indicates the shotgun Gauge bore size.
That's done with a pin gauge.
The '24' pin gauge is the largest that will pass thru the bore at a point (I believe it was) 10cm from the breech.
Not sure of the '26' mark.
The first Eagle is the Provisional Proof
Underneath is
Eagle + Crown/U together. This signifies the Diffinitive Proof (Final Proof & View Proof )
These are Black Powder Proofs...
The Crown/S signifies that the firearm being proofed is a Smooth Bore firearm.
However..Additionally, the gun was Re-proofed during the Nazi Regime. Sometime 1939 to 1945.
No exact date is within the more recent proof markings.
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The Nazi era proofing was done with Nitro powder (smokeless).
The Nitro bbl proof is lightly stamped forward of the BP orig markings on the bottom flat.
You can see the Eagle/N for Nazi Era/Nitro proofing
Below that is a faint '24 C(I?)' marking for the 'caliber'.
On the right side of the frame of the gun, there was also applied the Nazi era Nitro Proof marks.
...Eagle/N ,,Nitro Proof
...Old Style Eagle over Crown/N denoting Definitive /Final Proofing.
24ga shotshell gauge was a somewhat popular item in the early part of the 20th century in Europe. One of the inbetw gauges like the 32ga usually throwing a 1/2oz of lead or so..
In the USA , a few shotguns were mfg'd in the gauge. I believe Parker made a precious few. Most of those found are European origin and you can still find factory loaded shells with some searching.
More of a novelty as the 28ga and 410 have taken over the extreme small bore shotgun market for some time.
