I own a condo that I am selling. Showed it tonight and the potential buyers asked how old the unit was. It is a Tempstar SP80 but I have crawled all around the unit looking for a plate with a serial or date. Cannot find one. Does anybody know the date range that this model was made so I can at least provide some usefule input to the potential buyer? Thanks for taking the time to respond.

That model number has been used for some time over the years. The only exact way to know would be if you can find the EXACT model and serial number.