A perhaps curious (to some?) case of handedness is obvious among trades/crafts people in my area in the case of "metal snips" used quite commonly.
Called "aviation tin snips" (although almost nothing in the aviation industry has tin in it) the "compound lever metal snips" come in left-hand, right-hand, and "combination" versions, and it's common for them to be sold in sets of all three.
The "right-handed" ones have the blades arranged, and a relief on the upper blade, so that they easily follow a curve that turns to the right. The blades "point" at an agle to the handles so that the hands will be well above what's being cut. They're not particularly efficient for a curve to the left. The right-handed ones always (traditionally) have a green handle.
The left-handed ones have the blades reversed so that they follow a curve to the left easily, but don't work well if the curve goes to the right. The blades are at an angle to the blades so that the hand clears. The left-handed ones always have a red handle.
The "combination" ones have symmetrical blades so that they are a little easier to use to make a straight cut, but not too suitable for other than very gentle curves in either direction. The blades are on a straight line with the handles. The combination ones always have a yellow handle.
Virtually everyone who does "mechanical" work in the aircraft industy has a green handled one in the tool box. Perhaps 10% might have a yellow handled one. Red handled ones are extremely rare.
Although an explanation for the relative popularity of the three kinds should be left for a question on the quiz at the end of the class - - -
The reason that few people have both red and green (right and left) is that either one is sufficient. If you use them with the handles above the piece being cut, the curve goes one way; but if you put the handles on the other side the curve is reversed. (Pause to think and it will be obvious.)
If it's inconvenient to "cut from the other side" you can almost always turn the sheet over and lay out the curve on the other side of the sheet.
Since the "right-cut" (green handled ones) give better visibility of the curve you're trying to follow if you're right handed, the "green" ones are more popular. Since there's no need for both, and either will do, there are lots of green ones the "lefties" can "borrow."
It shoud be noticed in this case that it's the tool that has "handedness" and it makes no difference which hand the user favors.
Quite obviously there's no such thing as a "curve right" or a "curve left" if you look at it from the other side.
So by extrapolation, we may conclude that those odd people are not left-handed. They're just upside down.
As a side note, these snips are commonly called "Dutchmans" because the original maker (pre WWII) was named "Deutsch Mfg." Someone might holler "gimme a green dutchman" and everyone would know what was meant.
The original maker is now called Wiss," but I don't recall anyone yelling "gimme a green wiss" on the shop floor. (Sometimes it's best to respect traditional names?)