This is a very strong magnet & I assume it is from a machinist – I think it is a magnetic Chuck – I have taken photos with a ruler so that you can see size. It is grey & reads 007 – shown in last photo. It has 3 strips on the bottom. Measures 8″ around & about 2 3/4″ across the center. It is so strong. I put it on my metal table & i had a really hard time to get it off!