There was some discussion on how easy they opened the schakles somewhere,but I could'nt find it again.
Anyway,and I am no expert on this,watching a bio of Billy the Kid that handcuffs with ratchets had just been invented and had yet to make their way to the American West,thus Billy got out of the old style easily.
So it is possible ,maybe, to have gotten out of real old shackles with only the aid of a manicure set.
If you watch the movie again you'll see they didn't use a nail file from a manacure set but a small metal file. The iron used for shackles at that time was softer than modern metals. They also break the file in two. With all those people though it would still take some time and probably much longer than they allude to in the movie.
shareModern handcuffs all use the exact same simple key!! It's just a simple square on the end of a shaft.
The common key is simply so that any police officer - or wise guy with a paper clip - can open the lock!
It's one reason why nylon zip ties are more commonly used today.