The proprietor of the second knife shop in Salamanca I found these in asked if I wanted one for chopping or fileting. They come in two varieties, with the spine of the chopping variety about twice as thick, and much heavier feeling.
Your description and the photos sound like my knife - the spine of the knife is very heavy. I bought it in Madrid but looked at some in Toledo as well. I can't say that we actually use it any more. I have little need for a cleaver and use the Shun if I want a chef's knife.