yamilah:
a 'dolphin' (in Le Secret d'Hergé by S. Tisseron, 1993)
Actually, the description is in fact accurate, when used in relation to heraldic art.
Quite obviously from just how
inaccurate a depiction it is, the Mediæval scribe or herald who first drew a dolphin had never
actually seen one, but that was their idea of what a dolphin looked like, so that is how they are drawn on traditional coats-of-arms (modern heralds may choose to be more accurate, I don't know).
They are found in sculpture too - and were a staple of manufacturers of ornamental lamp-standards, if many of the lights along the banks of the Thames in Chelsea are to be believed.
They also are very prominent along the water-front in Geneva, so they made it at least as far as Switzerland, for our Swiss clairvoyant.
glendale:
I thought the Marlinspike chateau originally belonged to those two brothers (secret of the unicorn)and Nestor was also their butler.
Yes, but you seem to have overlooked that, as Mikael pointed out above, Sir Francis Haddock (the Captain’s ancestor) lived there centuries before the notorious Bird Brothers (and Nestor) did - it’s a major plot-point of the story; that’s why the Captain wanted the house, and why the Professor bought it for him.
Presumably (given that it appears to be part of the architecture) Sir Francis had his coat-of-arms incorporated into the house when it was built, and no subsequent owner had it removed.