My house had coax already run throughout (for cable TV) when I moved in over ten years ago. How would I determine whether it is RG-6 or RG-59? I've checked the cable for writing and I don't see anything saying "RG-6" or "RG-59". If it's RG-59 I think I'd like to replace it while I have a few walls opened up for a construction project.
The dialectric of an RG-6 is larger then that of its 59 counterpart. It could also say 59-u. Cut off a short lenght and compare it to a piece of coax you know to be RG-6, ie: at an A/V store which has a spool of RG-6 available. Since the walls are open, i'd suggest pulling new RG-6/RG-6quad. The upgrade won't hurt.