Does it have the original bail and pan? A substiution, lighter or heavier than original could impact zero.
This. Each bail and pan is “regulated” to the scale using varying amounts of lead shot in the bail. He may have mixed up parts at some point. I’d zero as best I could. Then add or remove shot from the bail to fine tune the balance. Of course, do this using your check weights included with the scale. If you don’t have check weights, use a bullet of known weight.
