pgtips,
First, welcome to the LTG forum! I'd love to see some pictures of your F312!
Second, this discussion has come up fairly often around here. Sometimes it gets a little contentious, particularly if someone is trying to sell something... If I recall, a few of the experts thought Brazilian was not commonly used after the late '60s, and that some early '70s guitars might have EIR backs but Brazilian sides. I have a '71 F50R that might be one of these, but I haven't really checked it out.
You can actually take some fine-grain sandpaper and rub the inside of the guitar somewhere hidden and do a sniff test. It may not be conclusive, but I hear Brazilian smells a little like bubble gum. I dunno.
Again, welcome aboard!