By Ajit Krishna Dasa
Jayadvaita Swami admits that it constitutes evidence against making a change if Srila Prabhupada read and/or lectured from a translation or purport without objecting to it:
“And yet we have several places where Śrīla Prabhupāda speaks of chapter six as the “Sāṅkhya-yoga chapter,” and of course he saw the chapter published with that title and never objected.”
The above quote is from Jayadvaita Swami’s annotated scans: Chapter Six from J. Swami’s edited copy of the 1972 edition. This is a chapter from the copy of the 1972 edition of Bhagavad-gītā As It Is on which Jayādvaita Swami marked the revisions for the edition of 1983.
Direct link to the annotated scans of Chapter Six (look for the headline “About sankhya”):
http://bbtedit.com/gitafiles/72_Gita_showing_revisions_06_chapter_6.pdf
Arsa-Prayoga 
The article was also featured on the Sampradaya Sun:
http://www.harekrsna.com/sun/editorials/02-18/editorials15788.htm