I had picked up a few steelyard scales. These were very popular for hundreds of years (they are also known as Roman scales). The items to be weighed hangs below the fulcrum on one side, while you slide a counterweight across the long arm on the other side of the fulcrum. They came in either a single range, or you could flip the scale over and hang from an alternate fulcrum to read on a different range.
I have 2 of the smaller scales. These look to be made the same. Neither has a mark. You can weigh items from 10 to 50 lbs . . .
. . . or down from 0 to 10 lbs.
One scale has a little surface rust and uses cast hooks for the fulcrums . . .
. . . while the other had a black painted surface with rings for the fulcrums.
As you flip the scale over to use one range the arm is graduated for the lower scale . . .
. . . and when you flip it over for the higher range it will be graduated for the higher range.
Surprisingly, these were accurate to within 1 notch.
I also have a larger one which can be used for much larger weights. I still need to check this one out.
The wife has some packages she wants to mail out. These would work great to help estimate the postage!