Some of the numbers on the bbls are a bit hard for my old eyes to read. The 20.5/70 shows the small end of the chamber measured 20.5mm (.807") in diameter & were 70 mm long (2 3/4". .807" is smaller than present day SAAMI specs for minimum chamber Diameter, so if you put a modern chamber gauge in the chamber it will almost certainly show it ass being short chambered, which would not be the case. The bores (At Proof) measured 18.3 mm (.7205"). I can't make out the choke diameters for certain, but perhaps they are 17.3 L & 17.6 R. if so the left barrel choke was .681" or about .0395 constriction (Full). if the right was 17.6 then it measured .693" or .0275" constrition (3/4 choke) or improved modified.
