I can only find 10 redundant latters, which fits nicely with the theme. Is the reference to there being 11 a typo?
I'm a bit surprised no one has asked for help parsing the second word of the clue to 35dn, which must mean it's obvious to all but me. And like others I shall be interested to see how the seven-letter date can be depicted accurately by the object.
Thank you both. My extras were 10x S, and I hadn't thought there'd be any different letters. But of course N has to be the other one. Not enough lateral thinking!