Leonard Ear Oil is the first patent medicine in the collection that I found that was condemned as useless by a medical authority.
 In 1925, DR. ARTHUR J.CRAMP (Director of the Bureau of Investigation, American Medical Association) condemned Leonard Ear Oil and eardrum as useless quackery and commented, “The fact that manufacturers of such useless productssucceed in a financial way is an interesting commentary on thelow level of human intelligence that exists in certain classesof our population.” 
The insert in the box with the oil states, “while not claim is made that every case will be helped, it has been successful in bringing relief to many troubled with conditions of this kind”.  Conditions of this kind refer to “chronic catarrhal conditions…that interferes with the drainage and ventilation of the nasal passages, mucous accumulating and blocking the Eustachian tube”.
Directions for use involve putting a small amount of the oil (ear oil?) in the nostrils and rubbing it on the neck behind the ears.  I guess this makes sense because the ingredients are camphor, oil of eucalyptus, spirits of ammonia, (mixed with highest grade of mineral oil), all of which will certainly clear your sinuses.  The insert also suggests treating earache with heat and wax build-up with hydrogen peroxide not Leonard’s Ear Oil but says that the Ear oil could be tried for rheumatic or other pains by rubbing it into the affected part!
Leonard’s Invisible Ear Drum looks completely bogus. I am including the part of the insert that describes it.  Judge for yourself.

The A. O. Leonard Co. seems to have been somewhat successful for at least a couple of decades.  The box states that it had successful sales since 1907 and it was still advertising in 1929.  The company seems to have originated in New York but did have a Canadian distributor in Toronto—Maltby Brothers, Limited.  The company is no longer indexed on the Internet.