I would just recommend that the owner’s do their own due diligence in regards to the home.
Glass thickness says it all. The thicker the glass pack/ insulated unit, the better u/r value. You could write it as although the windows are functioning as intended the may need upgrading to ensure full energy efficiency, or something like that.
Dendrochronology, Doug. First you take an increment borer and get a core out of the 2x4. This sometimes involves shasing the 2x4 around until you catch it, then holding it down with your foot while you drill.
Once you get the core you can then compare the tree ring patterns in the core to photographs of core samples in the data base of the International Tree Ring Data Bank http://hurricane.ncdc.noaa.gov/pls/paleo/fm_createpages.treering to come up with a date. To have this done by an expert is about $150.00 and you can just tack on $50.00. If you have to remove the 2x4 to drill… I guess prices vary some. I’d charge by the lineal foot.