The "APS" film cartridge appears to be the familiar 35mm cartridge, althouth the original concept included "indicators" that haven't been present on commercial 35mm film packagings for decades.

For 35mm cameras, you received a new film with the film sticking out of the cartridge, but you must rewind the film back into the cartridge before opening the camera.

A few "nut cases" I've met insisted that you needed to watch the frame count and stop rewinding as soon as it went to zero, but most people just wound it until it was all completely inside the cartridge.

The "remover" that made the film stick out again so that it could be pulled out for processing was just a little pin with a slot in the end to engage the center shaft of the spool inside the cartridge. Commercial proccessors usually had a machine to spin the film back out, and in later years the film was "ejected" directly into the "processing machine." In ancient times (15 years ago or so) most smaller processing labs just used a stick with a knob on one end.

If you turn the spool, the film almost always will reappear and stick it's nose back out of the slot in the side of the cartridge.

It would be reasonable to expect that turning the connection that the camera grabbed to rewind the film into the cartridge, but going "backwards," would be quite likely to induce your film to poke out of the can. (About like the way that hitting the outhouse with a hedgeapple always made uncle Ferd stick his nose out, except that the film shouldn't yell obscenities and throw the apple back at ya'.)

With 35mm cartridges you usually could accomplish the "winding" by just pressing a pencil eraser agains the "hole" and twirling. Stubborn cans might require you to push the tapered (sharpened but with the lead tip broken off so it didn't "bottom") end of the pencil into the hole. If you open a camera and look at the hole where you'd insert the film, you should be able to see the end of the "rewind shaft" poking up, to get an idea of what a "real" ejector shaft would look like.

In the fairly rare event that the film gets "hung" inside the cartridge, you would likely just pry one end off of the cartridge, which would normally destroy the cartridge. Reloadable cartridges were available, however, with an end that screwed on and could be easily removed and replaced. I suspect that they'd still be around for 35mm film, so that you could replace a can that you had to destroy; but they'd likely be difficult to find.

It was extremely rare in the US for a processor to rewind the film back into the cartridge after processing. The film was completely removed (detached) from the cartridge and after processing was nearly always cut in 4 to 6 frame strips that were returned in paper or plastic protective sleeves. Commercial processing machines used here usually cut the film automatically as it came out of the dryer, just as they cut the pictures apart as they dropped out.

Here, a cartridge with film inside but no end sticking out would mean that the film had been exposed but had not been processed. Ejecting the film, or opening the can, except in total darkness likely will destroy any images on an uprocessed film.

If you have a "genuine" APS cartridge, it should show a little "square" on the bottom that indicates that the film has been processed, but its been a very long time since any such cans were common in the US - so far as I've seen. If yours shows anything other than a square, it may have been rewound but not processed, in which case you'd need a processing lab to do anything before you mess with it.

John