I wish I'd asked about the 1952 when I made a Freedom of Information Request in 2011. Joseph Payne, the then Assistant Curator, said with regard to the 1954, that he was unable to say for certain whether only one had survived from a trial run of several hundred (the rest of which were presumably melted down).
That post is here
Unfortunately, I don't think he's there any more. He supplied a very cogent reply within a few days. The last two I've sent weren't replied to for several weeks and were pretty awful - the respondents clearly didn't have a clue how to answer my questions.