You'll hear some Prussian Dalys referred to as Lindner Dalys. Yours comes from the post-Lindner period. Daly experts might chime in as to whether that makes any difference.
The two 20's: One is the gauge of the gun, as in the shells you shoot in it. The other indicates bore diameter. All 20ga guns don't necessarily have the more or less standard 20ga bore diameter of .615. I had a somewhat later German 20ga than yours from Sauer. Mine had a 19 in a circle, in addition to the 20. That meant it had the bore diameter of a 19ga, or about .625 if I recall correctly, even though a 20ga gun. If you run a bore and choke gauge in the barrels, knowing the factory bore diameter will tell you whether the barrels have seen much honing.
