With the seemingly endless ways publishers have for stating a true first edition, knowing if a book is a "1st/1st " can be quite a daunting task. And a mistake can some times turn out to be very costly.  So I hope this list can be of some help.  If you do find it helpful please let us know at the bottom of page. 

Here are  many of the ways publishers denote 1st printing;           

                     1            

                     A     

                ABCDE   

                 12345   

           ABCDEFGHIJ

            0987654321

            1234567890   

           12345678910   

           10987654321    

           13579108642

             246897531    

              24689753  with stated First Edition  (2nd print will not say First Edition but have the same number line)       (Random House)     

  Harper & Brothers. Prior to 1912, the date on the title page should match the last date on the copyright page. They began stating "First Edition" on the copyright page in 1922. A letter code for the month and year the book was printed, which would actually be earlier than the official publication date, was introduced in 1912. In most cases for first editions published between 1912 and 1922, the letter code for the year on the copyright page should match or precede the date on the title page. J was not used.  -1st letters- A= Jan, B= Feb, C= Mar, D= April,  E= May, F=June, I= Sept., M= Dec  -2nd letters- M= 1912, N= 1913, O= 1914, P= 1915, Q= 1916, R= 1917, S= 1918, T= 1919, U= 1920, V= 1921,   W= 1922, X= 1923, Y= 1924, Z= 1925, B= 1927, C= 1928, D= 1929, E= 1930, F= 1931, G= 1932, H= 1933, I= 1934, K= 1935, L= 1936, M= 1937, N= 1938, O= 1939, P= 1940, Q= 1941,  R= 1942, S= 1943, T= 1944, U= 1945, V=1946, W= 1947, X= 1948, Y= 1949, Z= 1950, A= 1951, B= 1952, C= 1953, D= 1954, E= 1955, F= 1956, G= 1957, H= 1958, I= 1959, K= 1960, L=1961, M=1962,  N= 1963,  O= 1964, P= 1965, Q= 1966, R= 1966.

Harper and Row put the number line on the last page for awhile in the 70's.

   Some publishers , for example Knopf  only state 1st edition. and don't state a printing unless it is a later printing.

    Others  state only later editions.     

    Some can be way more complicated , such as having 1 - 6 then year numbers like 95 96 97 98 99,  the lowest year being the year of publication.

    Some  have a "first printed" date that will match the printing date of the book

    And with a lot of older books , match the copyright date to the printing year. Or  the date on the title page should match the one on the copyright page.