Frary's Spring Balance?

Most of the sites say this is an 1850s-1860s meat scale. I know nothing on scales, so I'm curious about when it was made and for what it's purpose was. I picked it up thinking it to be an old fish-weighing scale.

What is interesting about this Frary's Improved Spring Balance is that it increases by increments of 8 till it hits 40, where it then jumps to 50.