Isadore Nimeroff, 60, a retired National Bureau of Standards physicist and a credit union official for many years, died of a heart attack May 7 in Towson, Md.

He was stricken while attending a meeting of the Maryland Credit Union League, of which he was a board member.

Born in Philadelphia, Mr. Nimeroff received a degree in physics from George Washington University and later took graduate work in technical optics at the University of London.

He had joined the National Bureau of Standards in 1940, and returned there after serving with the Army in World War II. He retired in 1976.

Mr. Nimeroff's work was in the field of appearance of objects and materials, specifically gloss and color. He had developed an international reputation in a branch of colorimetry, known as metamerism, which deals with the difference in appearance of objects and materials when illuminated by sources of the same color but of different spectral character.

Mr. Nimeroff, a member of the National Bureau of Standards - Harry Diamond Laboratories Federal Credit Union, served as its president for 17 years and a board member for 19 years.

He was a former president of the D.C. Credit Union League and a former national director of the National Credit Union Association. When the National Bureau of Standards moved from Washington to Maryland, he became a member of the Suburban Chapter of the Maryland Credit Union League. He was elected to the Leagues board a year ago.

He is survived by his wife, Anne, and a daughter, Phyllis, both of the home in Bethesda; a son, Louis, of Kalispell, Mont., and sister, Jeanette Milakofsky, of Philadelphia.