Interesting...But I would think
(from watching Pawn Stars 
) that the construction of the canister, coloring, and method of attachment, plus the type/composition of the paper, ink, and method of printing, font, size, and irregularities would provide some kind of clue as to sender or recipient...
'Homing Pigeons' don't fly around looking for their owners; they fly from the release point to their home...If that chimney isn't the home or the release point, then logically it should be on the route to the pigeons home...
Language is another problem...Even if decoded, is it in English, German, Irish, Spanish, Russian??? Or even some other language...England has had many enemies over the years...
Frederick Forsyth mentions one of his spies using homing/carrier pigeons in one of his spy novels set in England...("The Fourth Protocol")...
