Hah! I don't remember. I did know a few years ago, when it came out. I think it was a combo of the age, and color of lettering, and some other identifiers. Don't remember if it specifically identified the contents as pappy. I'm sure an internet search would help. I never found the pappy stuff, but bought a bottle of their "limited edition" which has black wax on top, and red lettering on the yellow hued label. It doesn't have any "age" identified. It was a tad over 40 bucks. I am no bourbon guru, and am still learning what I like. I've experimented more with Scotch and Beer.
I thought it was good, but not fantastic. I also found that it tasted much better, TO ME, in a highball glass. I.e., in my mind, a very wide glass. Seems to need to breath.
I also tried adding water, and it didn't do anything remarkable except for making it a bit more approachable for a noob. I tend to add water (a lot) to most of my whiskeys at this stage in my journey.
At the time, if my grey matter is functioning, Black Hills was a bottler. Buying batches and labeling them. Seems to me I read that they were going to start their own production, but that is strictly my "memory".