Looks like the paint might be the famous "varnish by Dosseno Carlo" who painted frames for Guerciotti and many for Titan. Not everybody likes his artistic flights of fancy, but I do (or at least some of them), if it was my frame I'd try to preserve that paint.

Also never heard of a PRX tube set, but judging by all the bizarre one-off Columbus decals ending with "X" on Angel Garcia's Italian Cycling Journal, there were a load of these that appear to be custom sets made just for a frame brand (or at least the decals were!).