Validity of Share Certificate of Housing Society when it is not signed by the Secretary

In our society there is a person who claims that he is an Associate Member based on his name being included in the share certificate as per his application to hold shares jointly with the original member owner by paying an entrance fee of Rs.10.00 on 29/06/1997. On the share certificate his name is recorded but it is NOT signed by the Secretary although it is signed by the Chairman and Treasurer. Also the Society has not put it's seal alongside where share inclusion is recorded. Please note that the Share Certificate issued in the name of original member has signature of all three office bearers e.g. Chairman, Secretary and Treasurer and there is society seal put on the share certificate. However while including the name of the person as an Associate Member in share certificate there is No signature of Secretary and there is no Society seal has been put. My question is whether such change of including a person as an Associate Member is VALID?? I feel such an entry is invalid as the Secretary hasn't signed the same, although it is signed by Chairman & Treasurer. Kindly give your opinion.