I think the correct term would be incused lettering. These would be raised on the die, therefore any minute MD would not be struck away by a stutter strike.
Mechanical Doubling, as @Pickin and Grinin stated. Incuse lettering will actually be skinnier if doubled. Thicker incuse lettering is from the die 'bounce' or MD. This is opposite of what regular lettering/numbering is. Here are a couple good links to explain what you are seeing. Go to the bottom of the page to see the incuse doubling section. http://doubleddie.com/144822.html http://www.error-ref.com/incused-machine-doubling/
