Yes - that gun belongs in a punt. I would not advise shooting it in the manner shown for the picture.

The 1 1/2" bore (right around 1 gauge I think) needs to be mounted on a recoil absorbing rubber'd pintle to the gunnels for recoil absorbsion.
Seems to me, the 1 1/2" shot something like 3 pounds of shot with around 1,000gr. of powder - or perhaps more powder than that. I recall reading the record kill was 122 ducks and geese with one shot using 3 pounds of #1 shot - at a range of around 100yards to the centre of the flock. The shot was aimed some 4 feet above the birds so they'd take off into the shot cloud as the smoke cloud spooked them but was probably to allow for the rise and drop of the drop too. Pellets hitting the water only 40yards out would be wasted shot, helse the elevation given.

Fascinating guns.