In my opinion, of all Ben Graham's desciples, Walter Schloss is the only one who stays true to his value investing technique.
Walter Schloss believes a stock is a "good buy" if the company
1. Has no debt
2. Trading under its book value
3. The management owns the majority or big portion of the company
4. The business is understandable
5. Located in a country that has a security exchange commission or an equivalent "watchdog"
Did Graham state the importance of the factors above for Net Net stocks? All I could remember is Ben Graham recommended at least 30 stocks for Net-Net approach.
Warren Buffet started his investing career with Net Net stocks and I don't think he ever mentioned his criteria for selecting them.