Empire,
The Holland 10 bore Paradox was usually loaded with 8 drams black and a 925gr/950gr bullet @ 1450fps. 10 bore Paradox guns made in the nitro era were regulated with 55gr revolver cordite and the same bullet and producing the same ballistics. These guns weighed 13lbs.and had an.805 bore diameter. The above load will give approx 170TKO value (someone help me out if you have ballistics program with this calculation) and 160lbs of recoil.
The weight of the gun and barrels should give some indication as to what the load was or should be if no data is in the case or on the gun.
Frank Findlow's excelent article on 12bore, bore rifles has several charts comparing modern loads to various bore rifles. The DGJ vol.13 issue3 if you have it or can find it..