I have been trying to find thet answer to this same question and I am still not sure of the answer, so please regard this answer as speculative. The property apraiser has to find a way to assign a value to each property. To do this he/she will look at previous sales to get some idea of a likely price in today's market. However, some sales are not indicative of fair market value. Examples are short sales which might be way below market value, transfers to family members (which might show as $0.00), etc. These sales, I believe, will be coded as "disqualified as a result of examination of the deed".