yes 5 comics including batman #1 but he had used a gun since then as well. in batman 21, and several issued brandishing several different arsenal until the tv show and before that with the intro of baterang then only on occasion does he have a pistol or automatic weapon. in early 60's he taught robin to shoot robin had a riffle in one panel disarming a crook with some quick shots.
you are right the holster did only appear in 5 comics. I was wrong about the fact he stopped using firearms even though he claimed in several comics to not use guns then you would see him using them so a convenience lapse of memory on batman's part.
robin appeared in the 40's so that was not a huge jump since his 1st appearance in 1939. But in those times it was acceptable for batman to carry a pistol or have a Gatling gun in his batplane barreling down on a van, or appearing on 2 WWII covers holding a gun.
I'm only stating that you did the batman from 1939 and in 1939 he was toting a .45 pistol. I don't care what he did in 1940 because even if he droped the holster he was still caring a pistol.
what changed could be because bill finger and bob cane was finally giving batman a bio 6mo after the fact. not long after then the holster mysteriously disappears but his costume started to change as well. some say the 1939 batman was his father or a different guy sporting the batsuit to explain away how brutal batman just straight up killed people.
