Nishijin Shiroi Kamome with Sophia on the back - Model C - Can you help identify

[Thraka]

Greetings all! This is my first post and my first machine. I've never played on any pachinko machines and I haven't played this one yet. I found it at a local garage sale. It's pretty dirty and I would rather clean it before I use it. I've been tinkering around it and figured out how to open the panels and the glass. It's missing the key though. I've attached the pictures. After lots of searching on this site before posting my questions I found it to be a model C and it has the same background art as the one identified here: 1978 Boxing http://www.flickr.com/photos/vintage...7625127238867/

The center part is different though and features a nice bridge over a stream.

In my hunt for pictures to identify this machine I noticed that other model C's seem to have some sort of mechanism in the center back, mine doesn't Is mine missing?

I will continue searching for information but do you happen to have any bookmarked links you could share to speed up my search on taking it apart and how to clean it properly?

Here are the pictures. Thanks for any replies!
P1040057.jpgP1040058.jpg