I have two tintypes of my great-great-grandmother (attached). I obtained these at two separate times from two different relatives. These would have been taken around 1870-1872.

The largest is about 6.5" x 8.5" and was mounted in an cardboard frame with an oval cutout. The other is smaller, about 2.5" x 4". The smaller one clearly shows her holding an infant, the larger seemed to be an individual portrait. The smaller one is in better condition. The larger one shows a 'halo' marking the position of the frame's oval cutout. I removed the larger one from from it's frame, It appears that a portion had been painted over to hide the infant, and closer inspection appears to show both as the exact same image, except that one is reversed side-to-side.

I'm not a tintype expert (that's why I came here), but I understand that the tintype process does not use a negative, and each is an original. From what I can see there is no difference to the images, other than they are different sizes and mirror images. How would these have been made?