Here's my thoughts/stuff
Anyway, it could be true the writers of the show didn't know what would finally be in the G/S Ball if anything and that it would be a good excuse to get Ash in the Orange Islands.
Guessing by the clue that Kurt gave Ash & Co. (at the end of the episode where he said he'd keep it and study it will they got back from the Johto League) Kurt said that something along the lines of "some key must open it." Now, he may not have said it in those exact words, but, the way he said it, and, in the way they foreshadow events, it would seem that it can be opened somehow. When I heard this I figured that the thing in Ibex Forest would be the key.
Anyway, in the GameBoy Game Crystal Japan Version, you could receive the G/S Ball as a Key Item using the Mobile Adapter in the game. You would then show it to Kurt; he would keep it for a day; you'd get it the next day. Kurt says something odd is happening in Ibex Forest, you check it out, go to the shrine, and then Celebi appears. Now, one of TWO possible things happen here. The G/S Ball summons Celebi (makes him appear from wherever place or even time for that matter she is) or, it merely opens the ball. Now this is the gameboy game and not the Anime here, but why would they bother to include the G/S Ball in Crystal and give it an entirely different storyline?
So, maybe the G/S Ball doesn't have Celebi, but summons Celebi, right now that would seem to be the best argument for those who think the G/S Ball is empty. Maybe the ball itself has time traveling capabilities (Seriously). I personally don't know.
What do we know about the orgin of the ball? All Prof Ivy says is that they found it. Well where? In the gutter? If they were more specific there it might help, but they aren't.
Since no one knows what the G/S Ball is, it is probably from the past or the future. I think that it would seem to be more from the future than the past. Like maybe a future world has befallen a terrible fate, and they send something back in time (the G/S Ball) that might somehow prevent the disaster by warning the past about it, or hoping the G/S Ball in the past can prevent the disaster.
I know I have gone on a bit about this, but, I'm just sharing my thoughts on the Mysterious G/S Ball.
Ok, forgive me for doing this, but, I must debunk the theory that the G/S Ball is merely a prototype from the past of a Pokéball that doesn't work.
If the G/S Ball was just something made years ago that was a prototype for a Pokéball, then, there wouldn't be that much to it. It would be some kind of metal with nothing inside of it if the ball didn't work. If this was all true then the ball should be able to be opened by some means (lazers, chainsaws) and if the ball was simply a prototype scanning it would reveal it was an ordinary nothing!
The G/S Ball is meant to be opened somehow. There is some "key" that will open it. On the last episode in English that Ash still had the G/S Ball before agreeing to let Kurt keep it, Kurt said there must be "some key to open it" (or atleast he said something along those lines.) This is clearly foreshadowing of what is bound to happen.
So, the G/S Ball is something special that is not opening for some reason. I guess that it is like the sword in the stone situation. Only a chosen one can open the G/S Ball, or, only by being kissed by a virgin of royal blood (ok that's a stretch, but you get the idea.)
So, who made the G/S Ball and why is it here? I would guess that it is from the future and that someone from the future purposely sent it to the past so that someone would find it and be able to make sense of it. The G/S Ball may not be a Pokéball after all, it could be a device that somehow saves the world from certain doom. Let's say that the future world is plagued by some horrible peril (nuclear fallout, etc...)
Maybe someone managed to send the G/S Ball back in time and somehow the G/S Ball has the power to stop a catastrophic event from taking place.
Anyway, since Pokémon is about Pokémon, the logical guess is that a rare Pokémon is inside it. Maybe the G/S Ball is actually ancient (Forgive me for contradiciting myself). Maybe an ancient tribe who has long ceased to exist perfected the Pokéball thousands of years ago, and the G/S Ball was like a ceremonious Pokéball to them and they used it to capture one of the most legendary of all Pokémon.
Now, here is a HUGE kicker, what if the G/S Ball is holding a so called "evil Pokémon" that a group of elders sealed up in the ball years ago, and never was meant to be released. That could explain why the ball won't open, it was made to hold some horrible Pokémon for all eternity. Maybe, the 5th movie could be about Ash and Co. unknowingly release this Pokémon and having... [to]... stop it.
Thank you to all who read what I had to say really thanks.
P.S. Please reply with your thoughs & stuff, thanks.