It looks like a rolling indentation. Such errors should be underweight. Either the divot wasn't large enough to register, or this section of strip was slightly thick. Without the divot, the planchet would have been slightly overweight. Another possibility is two highly localized, rather thick plugs of grease that occupied the same spot on both dies. However, in that case, you'd expect a stronger design rim and a taller, more vertical edge.
Error coin writer and researcher.