I didn't have the correct key, but got mine apart without much difficulty. The hatch lock clocks in two positions, one 90 degrees from the other. You have to align the wafers with a channel in the sleeve. Here are two photos showing the inside of the sleeve, one taken, and then the sleeve rotated around 180 degrees and another taken. Note the channels:
The two channels in the first pic have "walls" at the far end. The other two channels do not - they are open channels from front to back. With the correct key inserted, the tumblers all retract, and pushing the large wafer in is all that is needed. Without the correct key, you may have to push the larger wafer down, and then insert a thin object like a hard wire that has been flattened to push all the wafers into the cylinder, so they will clear the "wall". Or, use it to push the wafers into the cylinder while you rotate the cylinder in the sleeve until the wafers fall into one of the channels without the wall. Then slide the cylinder out.
The good news is that after you replace the wafers with the correct ones for a key you have, assembly will be much easier!