If central government organisations have occupied your land for over 50 years, claiming compensation now is likely time-barred. While the Land Ceiling Act, 1976, allowed for compensation during land acquisition, a significant delay makes claims difficult. However, by filing an RTI with the District Collector to ascertain the acquisition law, notification procedures, and objection handling, you might uncover procedural irregularities. If due process wasn't followed, consulting a local lawyer to explore civil action or a High Court writ petition could be an option.