The photograph on the left shows where this revolver gets it name. When the latch on the top of the barrel assembly is pulled in an upward motion, the barrel and cylinder can then be rotated in a downward motion. When this is done, the expended shells are ejected leaving the cylinder empty and ready for new rounds. The picture on the right is of the cylinder after it was removed from the revolver. The ELG in an oval at the bottom of the cylinder is a Belgium proof mark which is why I believe that this revolver was made in Belgium even though there is no manufacturers name on the firearm.
Every barrel that was delivered to the proof house were first inspected , the caliber or gauge was measured, and according to this, the proof loads were developed. After proof firing, the barrels were inspected once more, and the inspector affixed his mark to the barrel after he was satisfied that the barrel was still serviceable. The inspector mark consisted of a star above one or two capital letters, A, N, AE,(An interesting note is that all of the inspectors names have been kept secret.). After this, the temporary acceptance mark was placed on the barrel or gun. Once the firearm was finished, it was then re-inspected and then marked with the final proof mark, the ELG in an oval. This final proof mark, like the ELG stamp above, is placed on firearms built after 1810 and prior to July 11, 1893. After this date, the final proof mark was modified to include a crown at the top of the oval. So judging from this, we can tell that the revolver on this page was produced some time between 1810 and July 11, 1893.
On the left hand side of the cylinder in the picture on the right, there is a star above a pair of brackets stamping. As of this writing, I do not know what this marking should indicate. This marking is also found on the barrel.