I would look carefully at your provenance also, since there look to be some later pieces on this bell. The threaded wingnut and the nut under it look like modern machined parts and I would not expect an 18th century hand forged piece to be able to adapt to modern hardware as it would not have had machined threads. Maybe some parts have been added later, but you will want to know what is what before trying to value it.
You will also want to determine the material it is made from. Typically bells were made of bronze, not of brass or iron, as bronze produces a sweeter tone.