"Was the Nikon FM3A a professional camera or a consumer model?"

Well, to whom? Moreover, for a user what difference does that make by just "being considered" as a Pro model?

Now, seriously speaking. FM3A was NOT built as a pro model. Please do not take durability and reliability as the only measure to differentiate pro models from consumer models. A pro models has to offer far more than that. Neither was FM3A marketed as a pro model. Although, Nikon designed and manufactured FM3A to take a lot of beat, the camera was targeting serious amateurs. For many pro though, FM3A is a great backup body.

Just some historical facts for your information.