Difference between McIntosh MR65 and MR65B

Does anyone know how to tell between the McIntosh MR65 and MR65b receivers. I know the 65 is mono and the 65b is stereo. Mine has MR65 on the rear panel but is (and says) stereo on the front.
I am assuming it is a 65b then..?..??

Also, was this the first McIntosh stereo receiver?

Thanks for any help!!