The coordinates will take you to a circular bench that was once the location of a National Savings and Trust Company branch (and later a Suntrust bank) near the McLean Gardens neighborhood. The National Savings and Trust Company financed a significant portion of the nearby Washington National Cathedral. The 1968 map below shows the location of the original circular-shaped building.
You'll require information from your surroundings near the circle bench to find the physical cache (a nano) a short walk from the bench. Have a seat and look around.
N 38° 56.A9B W 77° 04.C8D
A = third digit of street address of "Dalton Brody Fine Gifts"
B= sum of numbers of nearest numbered street (look across Wisconsin) - 2
C = second digit of street address of Dalton Brody
D = number of seats in circle bench - C