Isaac Abadie’s gate-loading system was a significant improvement in revolver technology in the 19th century, and Portugal was one of the first to adopt it. The initial Portuguese model was adopted in 1878 specifically for officers, and this was expanded in 1886 to a longer-barreled version for cavalry (the extra barrel gave about 10% more muzzle velocity). The detail of Abadie’s patent that was innovative was a mechanism which disconnected the hammer when the loading gate was opened. Thus, one could open the gate and then pull the trigger to cycle the cylinder one position at a time. This greatly sped up the process of loading and unloading the gun, since it was not necessary to exactly align the cylinder each time by hand. This would remain the faster-loading system for solid-frame revolvers until the development of swing-out cylinders.
In total, it appears that about 12,000 Abadie revolvers were made for Portugal between the two models. They remain very scarce here in the US, and I’d like to thank Mike Carrick of Arms Heritage Magazine for providing me access to this one!
For more detail on the Portuguese use of these revolvers, I suggest checking out the C&Rsenal episode filmed on the topic: