The Frontier is definitely smaller than the Excel 20. The Frontier is the middle model of the Pro Q products, smaller than the Excel 20 yet bigger than the Amigo. I'm betting that this cooker was a casualty of the Pro Q business that went under about 2 years ago. If that is accurate, then these are the older models and not porcelain coated. Meaning.....the finish will dull significantly if it is not stored correctly.
To my knowledge, these are getting harder to find NIB in Phoenix. They are decent cookers, but not for the asking price of $225. If you can get him down to $150, I'd buy it.
If you are looking for a Pro Q Excel 20, post a topic up here and ask if anyone is selling a used one. For some reason, there seems to be a lot of folks on here that use them.