This is a Miller Falls MF-07, with a 20 degree skew mouth block plane with the removable side plate for rebate work. Its equivalent to the Stanley #140, but with a much heavier, more robust casting.

This model was manufactured by Miller Falls from 1929 - 1970, with the one shown most likely post 1955 .Millers Falls Block and Specialty Planes Nos. 07 through 37



Typical with metal bodied block planes, and larger metal soled bench planes, moderate pressure only, is recommended by the manufacturer when setting the tension on the lever cap. Above that, and you will likely distort the flatness of the sole to a toe and heel down effect, let alone risk damaging the sole at its weakest point, the mouth opening.

The following photo shows the sole of this block plane after being flattened on 180 grit wet and dry. I have highlighted the worst low area, but as far as I am concerned those critical areas of flatness have been addressed, and there is no need to proceed any further.



The next photo shows the effect on the sole when too much pressure has been applied to the lever cap. Note the effect within the areas of the soles toe and heel after being worked to a dozen strokes over 180 grit wet and dry.



It should be noted that the abrasive pattern (shown above) also indicates some additional twist to the sole of this plane, most likely caused by a weakness within the design of the removable side plate.

The final photo shows the block plane after the blade was honed to 12000 grit, generating some fine curly shavings on hardwood side grain



Stewie;