@palmeride In the past, could Valentine have used his stand ability to send the soles of his feet to a different world, thus sending the sound of his footsteps to that world as well? Perhaps he just isn't bothering with that now.
To my knowledge, the earliest revolver that could actually be used with a silencer was the Nagant M1895, developed in 1895. I believe silencers themselves were developed in the earlier 1900s though. Somehow Magenta got his hands on them a few years early