The image above was sent to me by Alan Mansfield, and here is what he wrote.
“The ‘?’ on the UK promo copy of ‘Tears Began To Fall’ is interesting. I have looked at it under a 25x magnification printer’s glass and the ‘?’ appears to be printed rather than just stamped, this is borne out by the fact that the edges of the ‘?’ are clean and not smudges in any way, which would be typical of a rubber stamp. I have also seen the large ‘?’ on UK Reprise promo singles by other artists, and speculate that this was a way that UK Reprise highlighted their promos in the early 1970’s. Again, pure speculation. As you know, there are copies of the UK ‘Tears’ promo without the ‘?’ so why some had this symbol and others did not I cannot guess.”