Hello,

The reflecting light in the photo do not help to see if is a 0 or a 1 before the word poudre.
1.81 grams is equivalent to 28 grains, probably too much powder for a 16 ga.

In the photo I do not see a "70mm" mark, so you can not be sure if the barrels has 2 3/4" chambers or shorter.
If the chambers are 65mm then a charge of 24.5 grams seems more adecuate, I think.

Regards,

Jose M. Fernandez