All buttonholes consist of a series of individual stitches that are perpendicular to the edge of the hole and that run in parallel rows all the way around the hole. Â On a handmade buttonhole, those individual stitches will be thicker than on a machine made buttonhole, raised up a little higher, less regular, and there will be no space between them. Â This is a decent handmade buttonhole:
Though I have seen better. Â The better the work, the narrower and tighter the individual stitches. Â It takes small fingers to do it really well, which is why the very best butthonhole makers tend to be women. Also, on a handmade buttonhole, the underside tends to be unfinished, and rough-looking, like this:
On machine-made buttonholes, those stitches are straighter and more regular. Â Also, they are close together only at the edge of the hole; they get narrower away from the hole before going into the coat's cloth, showing a noticable gap. Â Also, the stitches will not be raised up as high from the cloth. Â Finally, the hole will look more or less uniform on both sides. I did not find a decent picture of a machine-made buttonhole, probably because no ebay seller posts them. Â They are, after all, not much of a selling point.