After reading the manual and searching the internet, it seems my view finder is different from most. As you see in the photo below, there's no release latch below the "ya" of the Mamiya logo on the front of the WLVF.
Check out this photo for reference to what I "should" be seeing
Also, my view finder looks kinda different while opened up as well; the loupe focus assist lens thingy is smaller. I'm guessing this is because my RB67 is a later model (it's just a Pro - not a Pro-S or Pro-SD).
edit: found the correct manual. I've now discovered that the finder is just stuck on there. The name plate will not slide to the right.