Revisiting this thread as I’ve bought a couple of very original -71’s recently and the various bracelet options got my inner geek going.
The first is a 31,6xxxxx serial, which according to ilovemyspeedmaster dates to Aug 71. It came with a 1039 that I fully believe to be original, with a 3 71 date stamp.
The second also has a 31,6xxxxx serial dating slightly earlier to June 71. This one has an 1175/640 which I again believe to be original and is date stamped 1 71.
The third has a 31,3xxxxx dating April 71 and is back to a 1039, again beloved original with a 4 71 date stamp.
There’s a couple of things I take from this.
1. 1039’s and 1175’s crossed over for a period (also suggested by the chart) and both can be contemporary to a -71.
2. Contrary to the widely held view that bracelets were often added at the point of sale, perhaps months or years after the watch was produced, this (albeit small sample) suggests that certainly during times when the Speedmaster was selling well (ie after the moon landings), the date stamp on the bracelet could correspond closely with the production date of the watch. Obviously the actual sale date could still be some time after both the watch and bracelet we’re produced.