NASHUA <NSH> TO PURCHASE PRIVATE DISC MAKER Nashua Corp said it signed a letter of intent to purchase <Lin Data Corp>, a private manufacturer of high-capacity rigid discs for storage of computer data. Under the terms of the letter, Nashua said it will acquire all classes of Lin stock for 24 mln dlrs. In addition, it said it will loan Lin 1,200,000 dlrs to support its operations. The closing of the sale is set for the second quarter of 1987, the company said.