PANMUNJOM, Korea, May 3 (Saturday) — lt;r.R) The United Nations and Communists made their 70th exchange of prisoner of war letters here today, with the U. N. handing the Reds 2161 letters for Allied prisoners in Communist hands.1st Lt. Harold T. Bradshaw,of Washington, D. C., actingU. N. postmaster here, receivedfrom the Reds 296 letters fromAllied prisoners in enemy handswho were writing to their families.The Communists also turned over 203 letters addressed to prisoners held by the V. N.The Allies thus far have given the Reds some 95.000 letters addressed to IJ. N. prisoners in North Korean POW camps.