Here are a few Dominica revenues from the Queen Victoria era, including a postally-used 1d from 1878 (by all appearances...it is struck with the A07 of the capital at Roseau):

and the 6d from the same issue:

and the 1d from the 1886 issue:

I didn't notice a note in SG that would've blessed the postal usage of the 1d, but if anyone has information to the contrary, please share.