quoteinvestigator.com/2017/09/25/progress/ on Quote Investigator says it appeared in 1948. Can't easily check, but will believe it for now.
Published as Scientific Autobiography and Other Papers by Max Planck translated by Frank Gaynor (1949) which also contained other papers.
This section refers just to the translation of Scientific autobiography by Max Planck (1948).
The Planck's law paper.
hermes.ffn.ub.es/luisnavarro/nuevo_maletin/Planck%20(1900),%20Distribution%20Law.pdf contains a replica of the translation present in The Old Quantum Theory by Dirk ter Haar (1967).
