I agree that halfs and quarters are often in almost perfect condition because they were easily lost soon after they entered circulation. I too look for nice examples, scarcer mints, errors, etc. and enjoy the challenge of identifying them.
This is one of my favourites. Walter (Waltier error) on Northampton, square E's on obverse (round on reverse), class 1a2/1a5 mule, possibly Mass 148, although the X looks different.