The postal rate won't help.
The rate for postcards was first set lower than the rate for a letter in 1898.
It stayed at 1cent from then till 1 April 1925, except for during WWI when it was raised to 2c to help pay for the war. (Nov2, 1917 to June 30, 1919.
I haven't found the exact details, but the rate for international mail of all types was stable by 1907. I would expect the international postcard rate to have been set at 2c and not changed for anything except WWI until 1925 as well.
I would expect the "place stamp here" to be earlier. 1907 was near the beginning of divided back postcards, before that one side was for the address and the other for the picture and message. Other countries like France would often have the stamp on the image side.
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