Photos are not great, but the case looks basically ok to me. Just worn, and someone has tried to do some sloppy amateur restoration. It could certainly be professionally refinished, if that's what you want.
A 7.1M serial 5513 will have an un-dated caseback. You will probably want a Maxi IV or Maxi V dial.
Read this:
http://www.5513mattedial.com/MaxiDials.html