State-run Cochin Shipyard Ltd (CSL) Tuesday said its board has approved buyback of equity shares worth up to Rs 200 crore."The board approved the buyback proposal for purchase of fully paid equity shares of Rs 10 each not exceeding 43,95,610 equity shares at a price of Rs 455 per share," Cochin Shipyard said in a filing to BSE.CSL completed its landmark IPO in August last year, which was a smashing hit, attracting more than Rs 1.11 lakh crore as against the offer size of Rs 1,442 crore.Shares of CSL closed at Rs 400.05 per scrip, down 0.53 per cent on BSE.