I have an oppurtunity to purchase a 125th Anniversary 25-3 that is listed as 45 ACP on its sales tag. THe SCoS&W only lists 45 colt varations of this commemorative. Is it possible that it is a 45ACP or just mislabeled?

Are there anyways to tell an ACP from a 45 Colt other than trying to close the cylinder with a loaded moon clip?

If you examine the pictures closely you will notice that on the .45 ACP revolver, the space between rear of cylinder and recoil shield is noticeably larger. Also, the cylinder locking notches are closer to the end of the cylinder than on the .45 Colt version.

The earliest .45 Colt versions (including, I believe the -3 model) used the shorter .45 ACP length cylinder as evident by the longer barrel stub ("forcing cone") in front of the cylinder. All later .45 Colt models used the longer .44 Magnum length cylinders, as evident by the shorter barrel stub.

Most likely mis-marked by the seller.

I agree. I have never heard of a 25-3 being offered in .45 ACP.

You can look into the chamber of either round from the rear, and easily see the difference. The .45 Colt cylinder will be deeply chambered, with a taper leading into a shorter throat, while an ACP chambered cylinder will have a shorter looking chamber and a sharp step at the end of the chamber where the case mouth butts up, since an ACP case headspaces off the case mouth.

Actually, there were 10,000 of the Model 25-3 revolvers made.

I had mine cut for moonclips, worked like a charm with handloads.