Happy new year.
The Colt Lawman came it 4 different flavors, 22 Long Rifle, 22 Magnum, 38 Special and 357 Magnum. (Edit: Note post #10 informs me that the Lawman only came in the centerfire versions and not the rimfire. Sorry about that, all. I got the Trooper and Lawman models mixed up.)
The "holes" (properly called "chambers") in the cylinder should be obviously 22 or 38/357. (22 LR is ever so slightly smaller than 22 Magnum, also called 22WMR) and either of these is easily distinguished from the .357" diameter chambers of the 38 Special and .357 Magnum. If the size of the chambers don't tell you, there should be markings on the side of the barrel that does.
Can you post pictures?
There must be an interesting story behind how you came by this gun. C'mon. Share.
The Colt Lawman series are excellent revolvers in any chambering.
Would you post what is written on the back of the 38 casings you tried? They might be a different 38. There are 38 Super, 38 S&W (which is a tad larger than 38 S&W Special) and others using the digits 3 and 8. Anyone who invents a cartridge can name it anything they want. Some of the inventors gave better names than others.
It is pretty hard to mess up a revolver's chambers. Almost impossible to make them SMALLER. Unless they need cleaning so badly that a proper cartridge won't fit. Far more likely is that the casing you tried to fit were fired in a gun whose chambers were slightly oversized. (Just a fact of life that some manufacturers, go large and some go small, even though they are within SAAMI specs)
Lost Sheep