It is due to the rotation of the earth this prduces a small centrifugal force that slightly counteracts gravity. Of course this only affects weights as measured by a spring balance and not those measured by a beam balance. these continue to be accurate because the gravitational weight of the weights themselves are reduced.

Er, no.

The weight of an object is the force that (local) gravity exerts on it. The mass is the same no matter how you measure it.

The problem is that a beam balance can't actually measure weight, it can only compare two weights. I can calibrate a spring balance by pulling a mass sideways and seeing how fast it accelerates. The force I need to use to accelerate 1KG at 1m/s is one Newton and I can then use that spring balance to measure forces (I can even do this in space where there's no gravity).

I can also use it to measure the weight of an object.

You can also use a pendulum clock to see the change in local gravity.