The three phenomena are fundamentally different, so easy to distinguish.
DIE WEAR affects the sharpness of every detail of
types and lettering, and is usually like a fog rising from the surface of the coin, blurring the lines where
types and letters meet the surface but allowing the higher relief to stay fairly clear. The
rev. of Robert's
Postumus ant. is a
good example.
COIN WEAR is pretty much the opposite: it immediately affects all of the HIGHEST points of the design and
legend, but leaves the coin surface and the less raised parts of the
types virtually
intact. If the die was in
good condition, the lines where
types and legends meet the surface will
still be
sharp even on a worn coin.
WEAK STRIKE means the dies were not hammered hard enough to force metal into the deepest recesses of the
types and legends. Usually it affects only one edge of the coin, so will be revealed by the contrast between the weakness there and the sharpness everywhere else. Moreover
weak strike must inevitably affect the same
area of the
flan on BOTH SIDES of the coin.