Export Publishing Enterprises Ltd began publishing its 156 title News Stand Library Pocket imprint in mid 1948. The first two books are unnumbered and undated. The reprint of Mark It With aStone states that the first printing was May 1948, with the reprint dated June. There is debate about which book is "number one" but I imagine they were printed and bound at the same time. I say this because they have the identical page count and binding - five stapled signatures, two with 12 leaves followed by three with 16 leaves for a total of 72 leaves or 144 pages. The reprint has six stapled signatures - one 16, one 12, one 8, one 16, one 12 and one 8. The reprint is 8-9 mm wider than the other two books.
Mark It With aStone was first published New York: Frederick Fell, 1947. Artists, Models and Murder by Toronto's Crown Novel Publishing in 1946.