Was General Custer left handed?
This photo of him at West Point shows him holding a handgun in his right hand.
This photo shows him writing with his right hand.
This nasty rumor was started by a Lakota Sioux blogger who wasn’t even at the battle and never met Custer.
As always, the victors get to write the history.
I read somewhere pictures back then were reversed like a mirror is when they were developed , so if hes holding that gun in his right hand, is he actually holding it in his left hand?
The way his jacket is buttoned should be a clue.
He was left handed but not left eardrumded.
Who do you think Paul McCartney was imitating?
This is not accurate. It is possible to reverse a picture, but except when done for effect, it would be an accident.
Note, for example, that the photo of Custer with a pistol has the buttons on the correct side of his uniform, not reversed.
In the one of Custer writing, there is a map of the US behind him on the wall. It’s faint, but the Great Lakes, Puget Sound, and the California coast can be made out. The map is correctly oriented.
The portrait of Custer on the wall, taken from a well known photograph of him, appears to be oriented correctly too. Here’s another image of the same portrait with Custer’s signature, indicating the original portrait should be facing right, as it is in the photograph.
This appears to be good evidence that Custer wrote right-handed.
The reason the question is of interest is the allegation that Custer might have committed suicide to avoid capture by the Sioux. From wiki:
Huh? What I see is a blouse which when opened will have the buttons on the left and the buttonholes on the right, which is the reverse of normal (male) clothing. Am I missing something, or are you mistaken?
Who was thick and yellow, and got slaughtered by the Sioux? 
The general, he don’t ride well anymore.
General Custard.
What’s thick and green, and can shoot a rifle really fast?
Custer wasn’t a general at Little Big Horn.
Wrong on both counts. The photo, taken in 1859 or so, was probably a tintype. With early processes, daguerreotypes, ambrotypes, and tintypes, the negative was the photo, and in a negative the image is inverted (basic optics). When developed the image is upside-down and the lights and darks are reversed. Photographers had methods to make the shading look correct, and making the image right-side-up was simple, but the image was then reversed left-to-right.
In that photo I cannot see the badge on his kepi clearly, but the buttons on his blouse are on the wrong side and the hammer of his Colt Model 1855 Sidehammer Pocket Revolver, well, that should be the side it’s on, but it’s not. The photo is reversed and he is, for whatever reason, holding the pistol in his left hand.
Maybe I’m just not following, but this sounds absurd. “The image was upside down”? And the plate couldn’t be turned 180 degrees for printing or positive pull because…?
The left-to-right inversion I understand, and I assume that it was a matter of printing through the plate to get correct left to right results. But the “upside down” throws me.
That’s what I get for looking at my shirt upside down. 
As to the photo information: regardless of the process, photographers generally knew how to produce prints that were correct–as demonstrated by this photo of Robert E. Lee.
ETA: Sorry, I failed to notice the tintype reference in which reversal was standard.
What you have is an object, a pinhole aperture, and a surface. Light bounces off the object and goes in a straight line in all directions. The pinhole acts as gatekeeper, only allowing those photons coming at it through, with photons coming from the left hitting the surface on the right, and photons coming from the upper part of the object hitting the surface on the bottom. When you look at the surface the image is reversed in both the X and Y axes.
You can correct the vertical distortion by rotating the image 180 degrees on the Z axis, and, as you realized, if the surface is transparent, like the glass plate used for the second picture, you correct the horizontal distortion by rotating the image 180 degrees on the Y axis and looking through the back of the surface. You cannot do that with an opaque tintype, so when you rotate yourself 180 degrees and hold the photo up against the object you will see it is reversed.
Oh, and as for your first question, because tintypes and daguerreotypes are made with opaque substrates, each is a one-off. No printing or pulling involved.
I’m still not clear on whether or not he was left handed but it should also be noted he was found with a injury to one of his arms. Was it his right arm?
He was right handed. I would regard the photo with his wife, in which he is writing with his right hand, definitive evidence of that. That photo is clearly not reversed, since the map of the US is correctly oriented.
It would seem that in the photo of him at West Point, which is reversed (from the evidence of the buttons and the gun itself), he is holding the pistol in his left hand. However, since this is a posed photo that’s much less significant than the photo of him writing.
According to this, the wound was to his right forearm.