There’s a third component to the “33” answer :
When I was in college, I was consuming some Rocks with friends and we started wondering about the mysterious “33.”
We made a long-distance call to the brewery in Pennsylvania and inquired about this to the receptionist. She put us on to a sales rep, who stated, and I quote: “33 is the year prohibition was repealed, the number of words on the back of the bottle, and the temperature at which you should drink the beer.”
Anybody who drinks Rock can attest that it magically transforms itself into the most delicious brew imaginable when drunk at an extremely low temperature. I suppose this is true of some other beers, too, but Rock ecpecially seems to shine when it’s near-freezing.
By the way, avoid the new Rock Green Light beer like the plague. It’s an aberration. Tastes like razor blades coated with aluminum foil–i.e. metallic. Horrendous.