That should help a little, its my semi-crappy case guide on my website. If it is a shaped LP case, make sure there are no extra pads on the inside. the true earlier cases look like the orange one pictured. Mine has 50s style latches as well. There should be no logo on the outside etc.
I dont know as much about the rectangle case.
When I bought my 69 back in the mid 70s, it came with the purple-lined case. The guitar is a mid-issue 69 based on its attributes, but didn't ship from the factory until Dec. 69. I don't know whether this case accompanied the guitar, or whether it was purchased later.