ifish4wildtrout--Probably last year's fish, although it isn't particularly easy for untrained folks like me to tell. There are too many imponderables--food base, competition for that food, presence of really big browns (they eat these fellows), fish numbers, etc.
The parr marks (or thumbprints as I have heard the rounded spots along the side of the trout described) leave no doubt of its lack of maturity. I might add, just to include a note of sheer heresy, that this is exaclty the size trout I want for the table on the relatively rare occasions when I eat a mess. It wouldn't reach the Park's seven-inch minimum, but in many N. C. state waters there is no minimum size.
Anyway, you obviously had a magical day.