You have to love DUATS!

I was checking local weather and saw this PIREP from Duats:

Denver CO [DEN]: pilot report
at Denver [DEN VOR] at 8:07am MST (1507Z), at flight level 430 a Piper
J-5 Cub Cruiser(L-14, Ae) reported temperature -5B0C, wind 294/062

I'd like to see the STC that gives this cub the ability to get up to
FL430! Isn't that too high to be wearing oxygen? So wouldn't it also need
to be pressurized? I wanna see this Cub! I have seen J-3, but what's a
J-5?

-Louis