Thomas Earl Diggin Sr., 69, a retired Army Department official who helped establish the Test and Evaluation Command at the Aberdeen Proving Ground, died of a heart attack April 10 while aboard the cruise ship Vera Cruz in the Gulf of Mexico. He lived in Bel Air, Md.

Mr. Diggin and his wife, Ellin LeGrow Diggin, were vacationing when he was stricken.

A native of Boston, Mr. Diggin graduated from Harvard College. He moved to Washington in 1941 and later earned a master's degree in management at Antioch College.

He went to work for the Army Signal Corps during World War II. In 1955, he joined the Post Office in Boston and helped regionalize its operations. He returned here a year later and continued his work for the Signal Corps. In 1962, he transferred to the Aberdeen Proving Ground, where he retired in 1972.

Mr. Diggin later taught business courses at Newark and Harford Community colleges.

He was program chairman of the National Association of Retired Federal Employees in Bel Air and a member of the Moose and Lions clubs and the Service Corps of Retired Executives.

In addition to his wife, of Bel Air, survivors include three sons, Daniel R., of Crofton, Md., John L., of Bel Air, and Thomas E. Jr., of Lanham, and one grandson.