I'll look around for the book. I'd like a good source. I have time and enjoy the hunt.
I've purchased most every gun I've ever owned used, so I've been pretty lucky, even in the Spanish area, thus far. But I try to be as informed as possible about the "market".
Related to Spanish sidelocks...I'm a big fan of mid 1950's Victor Sarasqueta's. I have a very sweet little 12E, 20 gauge, and a 9E,12 gauge. I feel lucky to own both.
I've traded around in others like Grulla, AYA, Arrieta, and I've enjoyed them, each for different reasons. I just like the history and the quality price ratio that those old Sarasqueta's deliver.