Norton HB6 / HM6 hard Arkansas oilstone

The stone comes in the original Norton box, either HM6 marked on the lid. The box is in reasonable condition but there is a piece missing from the end as seen in the photos

The stone itself has a blue Norton HB6 stamp

And measures 147 x 48 x 19mm

I have taken a photo against a grey Norton translucent Arkansas for colour reference only

Any questions feel free to ask