The rifle load which was the cause of the warning about .32-20 ammunition was the 80 gr. "High Velocity" hollow point load which was intended for the 1892 Winchester and 1894 Marlin rifles. The box carried a warning to not use in revolvers and Model 1873 Winchesterrifles. The bullet looks like a round-nose full jacketed one with a small hollow point in the nose, they are very distinctive.

This type ammunition has not been manufactured since before WWII, (possibly as late as the early 1950s, but I don't believe so), and it is highly unlikely you would find any of it.

All current manufacture .32-20 ammunition is suitable for revolver use.