Second gun is a .38, most likely a black powder .38 Long. Have the cylinder measured by a good smith. If it specs at .38 Long you can buy ammo for it from Track of the Wolf. Good round, I have a smokeless powder .38 Long Basque made revolver that is butter smooth to shoot. I have shot .38 Special through mine, DO NOT do that with yours, yours pre-dates cylinder tempering by a couple decades.
Official Police, like the Smith and Wesson M&P, is almost dirt common. Around here they run $400 or so depending on condition, but a primo example will fetch a lot more. M&Ps can be had as low as a couple hundred bucks.
The older gun around here would run from $700-1200 depending on its looks and operable status.