A couple of these showed up recently and I think that they are movie blanks made by a local special effects company. They were made using a CBC .45 Colt revolver case with a groove added and the rim turned down (bevel included). The knurled cannelure present in the original Colt case can be noted just above where the neck starts. Total lenght is 31.2 mm (1.228"). A most unusual transformation that looks almost factory made.
From the photo, looks like a highly professional job. I don’t recall ever seeing before a .45 auto caliber blank made from .45 Colt Brass. It is more common here to use .45 Win Mag cases, but then they probaly dn’t show up much in South America. Very nice round. Thanks for posting this.