737-40 CSS1131-34 with seldom seen cancels, on a post office bulk mail receipt and a scarce 1948 cover to USA with Nanking Mobile Post cancels YTT perfins and a 1947 cover to USA with five YTT perfins

737-40 CSS1131-34 with seldom seen cancels, on a post office bulk mail receipt and a scarce 1948 cover to USA with Nanking Mobile Post cancels YTT perfins and a 1947 cover to USA with five YTT perfins