It all depends when the notice was issued when the final settlement was done, what was the response of such principal, as there is a limitation period for every legal action. Contact a local advocate with entire correspondence on the issue on refund of such deposit and perhaps he may find a way, as principal never refuses to repay security deposit in response to notice and limitation period commences from the date of his refusal to refund such deposit and final settlement statement. You can plead for compound interest and it is the court that has to decide basing on the terms of such payment of interest stated in agreement. If the annual interest is refundable, and not refunded then a court may take into account compound interest.
You mean to say you will raise the calim after 25 years ; just you woke up like Rip Van Winkle....
First, conclude that you may not get the amount, and now as you have nothing to lose by spending few hundred, issue a demand notice as per directions of the local advocate. Depending on the facts of the case, there must be a way out.. If the security deposit account is showing your name in books and in the balance sheet as a liability, I think there may be a chance as showing such liability may amount as debt acknowledgment. Also, make some efforts by searching in google with keywords "Company not refunding the security deposit after the termination of dealership".