2 Early, Handwritten Neil Simon Letters Signed

2 warm, handwritten letters from Neil Simon (both signed "Doc") to a fellow comedy writer. One dated October 1963, the other from the same period if not even earlier. In both cases he's expressing his surprise over the success of his early plays (possibly "Barefoot in the Park", etc.). Both letters have held up very nicely, as have the original envelopes (with his New York addresses at the time prominently featured).