Im allowed to carry whatever duty gun I want, as long as its the issued Glock 22. I had to give up a Wilson Master grade Govt Model series 70 for that.
Before that, there was alot of Brownings, Colts, Smith autos a few Sigs and later, a few Glocks. Some of the guys still carried revolvers. The biggest problem was the dept provided training ammo. They had to stock .38 special. .357 Magnum. 9mm. .45 ACP. .41 Magnum. .44 Special. .44 Magnum. .45 LC (I know). (and later .40).
We were authorized to carry Dept shotguns, personally owned shotguns and carbines. So, add 12 GA and .30 Carbine to the mix.
The range guys had to inspect and keep up with a whole mess of different guns, but, if it broke, you were on your own to get it fixed.
From a purely practical standpoint, I understand the one gun, one caliber theory...but, there was alot more personality back in the old days.
A very good friend of mine works for Dallas. He still carries the S&W Model 66 he started with as a rookie over 30 years ago. He is one of the few left. He was grandfathered, we did not have that option.