Their 2 foot high fins vary in shape and size. Allied Whale has a photo catalog that divides the whales up according to six different fin shapes. All the triangular shaped fins are together, all the sickle shaped fins are together, all the whales with a hump before the fin are together, and so on. Each whale can be separated form the others using scars on the fin or anywhere on the body. A third feature that may be used to tell them apart is a color pattern on the side of the body.
Finbacks are the only animal in the world that are asymmetrically colored.
Meaning, one side of their head has color while the other doesn't. The left side is mostly dark while the right lower jaw is white and runs up onto the side of the head in a swirlish pattern that becomes a white, greenish, gray wash. The pattern is bright in some whales and faded in others. It is not known why finbacks have this coloring but it is thought that it may help them in catching food. It maybe that they flash the color at a school of fish to drive them into a tighter ball or maybe it hides them so they can move in and get a larger mouth full of food.