What is the significance of the piece of leather Manco wears around his right wrist?

El Indio doesn't give the piece to Manco. It's already his. In earlier scenes, you can see Manco wearing it. I imagine it's some sort of brace for the wrist to help with recoil, and also that it's the sign of a professional Gunman.

If you look closely in the scene (Edit: I originally linked a video; it's no longer available) at about 2:06:10, you can see El Indio throws up Manco's serape, then reaches to grab the brace, taking it from Manco and holding it up. "You shouldn't have shot the apples off that tree," he says to Manco as he holds the brace. The implication here is that such fine shooting was a giveaway that Manco was more than just a bandit. Then he tells him to put it on, and it fits, which proves to El Indio that Manco is a "bounty killer" as he says later.

The significance of it, is that this is the piece of kit that differentiates him from the characters Blondie, and The Stranger, from the other two movies.

Just as Colonel Douglas Mortimer wears his gun on his belly to differentiate his character from Angel Eyes (who does not). Because these movies were made on the cheap, with basically the same wardrobes, locations, and actors. Whatever 'marketing' did after the fact is meh IMO.

Why does he wear it? Because he shoots people for a living. If you've ever fired a hand gun, you'd understand why there's the phrase: "It kicks like a mule." You can always tell when actors are not firing live rounds: maybe I don't have the best gun control, but when I fire them, they're more or less pointing straight up at some point after the recoil. A wrist brace would help with that.

Indio saying, "Put it on." is like saying, own it; stop playing and show us who you really are: a bounty killer.

I'll take this opportunity to point out the fact that:

• Manco is a bounty hunter who respects the law.

• Blondie is a criminal.

• The Stranger is a drifter with a heart of gold.

NONE of these are the same guy. Neither are any of the characters played by Lee Van Cleef or Gian Maria Volontè. Unless you believe in spontaneous resurrection, them all having changed names, and having uncharacteristic schizophrenic tendencies.

Note, there are numerous other extras that play different charterers throughout, which does not help any case to contrary the above.

If you believe that Clint Eastwood is playing the same character in all 3 movies (because , unbelievably, some people don't), I've seen comment that he wears it as a brace due to his hand injury from A Fistful Of Dollars which would make sense.

I have long wondered about this. I decided just now to review everything I can. In Fistful, the LEFT hand is injured with a stomp from the heel of a heavy guy, after The The MWNN is beaten up. Later, while making his new armor, the left hand is consistently bandaged. Right hand has nothing, even in the final duel ... yet the left hand is still bandaged. When the MWNN is introduced in A FEW MORE, it begins with a closeup of the brace on his RIGHT hand, the hand which came through unscathed in Fistful. Puzzling. In A FEW MORE, the left hand is all strong and hearty. The brace on the right hand continues right up through the climax of A FEW MORE. IN GBU, I have been unable to find any images with a brace on either hand. However (to add to the confusion), the album cover for the soundtrack to GBU shows Blondie lighting a canon with his left hand, and a wrist brace is clearly on that left hand. But, that's just an artist's rendition. http://www.amiright.com/photoshops/images/album_1479278326.jpg And, at YouTube, I have queued the following link to show a cool explanation for the brace on the right hand.

My take: Continuity is always hard to establish across a series. Upon review, I am shocked to find how young, brash, criminal and unpolished The MWNN is in the beginning of that story. And he doesn't find a poncho until the very end, when this criminal finally shows some humanity, as he comforts a dying soldier. It would appear that GBU was a prequel, to explain his origins, and that Fistful and A Few More were the next logical stories. Of course, these arcs do not explain what happens with all that money he is scooping up along the way. But, I suppose we can think of something if we try hard enough. ==> The brace was applied to the right hand of this maturing character deeper, into the career of The MWWN, as it shows up in A FEW More, the last logical episode. That's the best I can do.