Zero error at the Cross Keys Temperance Inn

We went to the Cross Keys Temperance Inn near Sedbergh - a pub without beer! This was amongst the curios hanging in the parlour...

I love the fact that it calls itself a spring balance, like the ones at school. It's also made by Salters who are still in the trade. I was interested that it doesn't read zero with nothing hanging on. We call this a zero error and it would result in a systematic error because all readings would be out by the same amount. The needle is not flush with the scale so there is a parallax error - from the angle I took the picture it looks like 12oz but the shadow suggests 8oz would be correct. The precision is stated as +/- 2oz, although you should be able to read the wide scale divisions to the nearest ounce. It claims 60lb but the max reading on the scale is 20lb. Does it go round more than once? The wonderful Cherry Bakewell might tempt me back to find out!