You may need to refine the question. I think you are asking for the King's coat of arms at the time. The House of Bourbon in the 18th century included Philip V, Charles III, Charles IV. Their coat of arms are different from each other and show non-Iberian domains (e.g.). So that explains some of the variety you are encountering in your search. Also, there are lesser coats of arms, which add to the diversity and often show the Iberian domains alone (and maybe that's what you are looking for)