New project - mirror questions

I'm finally starting on a new project with an old mirror. It is a 10" ~f9.6 mirror with a very old coating. It was stored wrapped in a box with a UPS label - maybe it was shipped and the packing material rubbed and messed up the surface. Who knows? There are no obvious scratches, but the coating looks terrible - missing in several spots, sleeked in many others, and a big area in the middle that doesn't look a shiney as it should. Anyway, it has been sitting around for a long time because I wanted to get it re-coated before building. But I also wanted to test it's quality before re-coating. (And procrastination is easier.) So now I'm going to "throw together" a simple box/truss Newtonian to see what the images look like. My mirror questions are... Is this just an old coating or could something have happened to the glass surface that will make it bad upon re-coating? I have a ronchi grating that I will use to test, but are there other simple things I should do either in the garage or under the stars to test it before I send it off somewhere?

Thanks,
Charlie