Vintage Seamaster Chrono parts question

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Good morning Gentlemen and thanks for allowing me to join/ask a question.
I have a friend that bought his Seamaster Chrono brand new in 1967.
He had the crown replaced several years ago with a non-OEM crown.
One of the chrono hands dislodged itself and I'm going to have my watchmaker put it together for him.
Without opening the back does anyone know what model number crown I should pick up. They sell several NOS one's on ebay and I'd like to make sure I get the correct crown (with "O" logo) for him.
I'd also like to get a new acrylic crystal if anyone has a source. I suppose some polywatch would do the trick, but I'd rather get a new one that's unmarred.
Pics enclosed for reference.
Thanks so much!
Chris