Is anyone familiar with early Sony U-Matic VCRs?

[cjacek]

Hi,
I just rescued an old (but really clean and low use) VO-1800 Sony U-Matic VCR from the dumpster, been working on it for a few weeks and it's almost back to its former glory. One small issue: I need to remove the bottom cover/plate. I have unscrewed the 4 feet but there are still several screws left, with one being rather unique. Is anyone familiar enough to say WHICH screws need to be undone? I don't want to risk it by removing all these screws, in case something is fastened that needs to stay in place. Anyway, I'd appreciate some advice. Attached is a photo. Thank you.