Thanks to you all for your replies.
I must admit I had no idea of the collect-ability of Heuer watches and it's been an education researching the history of the 844 series of watches.
One question I have is where would you guys think the "Brevet" stamped case comes in the manufacturing time line, before or after the Monnin stamped case backs?
I will attempt to look for the original purchase invoice there's always a chance it could be found and will try and piece together where I was and what was happening back in the seventies as my recollections of 74/75 don't fit 844 history.
Graham