I remember years ago, someone on a gun forum said he always took high res pics of his new used guns. He said the photos showed way more than the naked eye. I bet these don't show up as well in person as they do in the pics.
Also, it seems obvious that one end is a smaller diameter. Should you decide to take the plunge, it should be easy to tell which end to hit.
That thing is a monument to industrial manufacturing of a bygone era. Obviously neglected, 122 years old and still quite a viable sewing machine. I'm going to go oil something ...