Thats really an amazing result!
Another example (with replace bezel but original bracelet) was sold two years ago at Phillips for 22k US:
https://www.phillips.com/detail/LONGINES/HK080117/826
The fact that many of you here on OF were interested in it or trying to bid shows that it is a highly collectible watch.
This year two Longines steel chronos were sold at auction for more than 100.- k (one for 250.-k). This means that the very few real rare Longines pieces have reached a price level that can be compared with Rolex.
Concerning the 6921: this is the the first diver made by Longines and it is very different to all other early divers (even some early Seamster 300 (
https://www.phillips.com/detail/OMEGA/CH080118/123) or Breitling Super Ocean,
https://www.phillips.com/detail/BREITLING/CH080117/94, have reached an incredible prices today).
The Longines 6921 has a perfect size and 40mm are rare for a vintage
The Longines 6921has a rare and unique dial, black galvanized with attractive hourglass and most important with "Explorer" type Radium numbers on dial.
The Longines 6921 has unusual and unique hands
The 6921 has an attractive back.
It was made in very small numbers. It is estimated that only around 300 examples have been made in 1959 within 3 series.
I personally did not see more than 15 - 20 examples showing up during the last 15 years (many of them in bad condition).
So may be (and compared to a 1959 Explorer Type Submariner.
https://www.phillips.com/detail/ROLEX/NY080117/33) it was still a "bargain"
😗 or at least worth this amount of money?