Kyrie,
If you walked into Greener's prior to the turn of the last century, and asked what his top model was, it was a boxlock. Some years later, that particular model of boxlock was gone, and the top model was a sidelock. He would, at that later time, build you a straight A&D boxlock, that cost less money than either the sidelock, or the Facile Princeps boxlock.
What I am asking is, was that ever the case in Spain? Was there a company that had, as it's most expensive model, a boxlock over the same companys sidelock?
Options don't really enter the picture. Neither does a base model boxlock, as that isn't what we are after. A few of the English makers believed the boxlock was the next, best thing, and built them as their top of the line gun for some time. Then, that time ended, (except, maybe, at Westley Richards) and the sidelock was the top dog, again.

Oh, the #2 you linked to has drop points in the stock-they are those stylish teardrop shaped carvings to the wood behind the lock plate. Good, English boxlocks from the era I'm alluding to do as well. Church windows refer to checkering that is in the area where the wood meets the back of the action on a boxlock. Very high grade American boxlocks will be seen with this treatment on occasion (think higher grade Parkers and Foxes) as will best work English boxlocks. I think it looks best with a sculpted action back. A very well fitted sculpted action back, by the way. I've never seen a Spanish boxlock with the pins installed for intercepting sears, but, the English did that on their best boxlocks.

What say ye, Kyrie?

Best,
Ted