I think what's 'missing' is an optional module that was sold separately as an accessory. I'm not sure what this module would have been. It might have been a dryer module, or it might have been an alternative or additional control module of some sort. As far as I know, the machine will work just fine without this additional module.
Here's a YouTube video from a series of 5 which seems to demonstrate the RCP50 without the additional module, and as far as I can tell, it works OK that way: