As for the Unicorn, you're aware that the template for Herge was a model of a French 54-gun third rate, second order (yes that's how the French during King Louis XIV, classified their ships!). I believe the model exists at the Musee Navale in Paris, but I've only seen pictures of it, and I did her years back as a paper, pencil drawing. The correct French terminology would be 3eme Range, 2eme Ordre Vaisseaux du Ligne. (1690)
"Le Brillant"... it is welcome a suitable reference.