I believe it was the Star D series they copied, started to under license. There was even a slick advertisement for the Colt Pony in Guns and Ammo or one of those gun magazines.
Colt contracted the manufacture of 50, and the story I read said they were not happy with the fit and finish and destroyed all but two, both are extremely collectable now.
The frame of the Star D model is the same exact dimensions as the aborted Pony, and the ignition train is the same I believe. The safety on the Star D looks different externally than the Mustang and Colt .380 Gov't model but internally it is a dead ringer.
BTW, there were two of the FI and or FIE models made, some say with Star made frames, I don't know. The one I had had a weird Zamak magazine bottom that made me want to vomit, I sold it right away.
I found photos today of an FI model D with the standard type magazine receptacle and magazine, it's hard to tell which one if any were made partially in Spain.