I have an old Potters Lead Hardness Tester.
I have downloaded the instructions for it.
The scale they use doesn't tell what the Bh is.
This is it...........
The following table is a guide for using the Tester:
2-1/2 Scale Reading is approximately 10 to 1
4 Scale Reading is approximately 15 to 1
5 Scale Reading is approximately 18 to 1
6 Scale Reading is approximately 25 to 1
Anyone know what the Bh would be????