I really love the story and history to your watch. Did you leave the engraving intact? I think it would be wonderful to see if possible.
Could you please PLEASE PLEASE show me a pic of the box and papers (So I can dream about what my watch had!).
I notice your coin edge is different to my 6405 - In the 1950s/1960s Vacheron only ever made 24 pieces exactly the same, hence the variations.
I am so impressed with your story.... your watch is the HOLY GRAIL of 6405s!
That movement (K1001) is a personal favorite.
Kind regards