I just picked this guy up the other day (Case Ref 14765 SC, 180xxxxx serial, Cal. 552 movement), sold to me with original dial/hands/indices/crown, with an unsigned crystal. Being the completionist that I am, I'm on the hunt for a NOS crystal. I've been told that PZ5072 is the part number for the crystal, but I'm seeing listings for it with a steel tension ring or a yellow tension ring - anyone have any ideas as to which of the two I should choose/is most correct? Thanks in advance!