Originally Posted by
Hyacinth 
If you read the description a bit farther down and the subtitle line right under the listing title, it's actually a genuine Carrier Brief style 9800 which is a little larger than a Musette but very similar in design and details except for having an outside back pocket and sometimes a longer strap. The seller is also a tPF member who authenticates any questionable or unusual bags here before she lists them.
The Musette was a much earlier design than the Carrier Bag, which was only introduced in the late 1980s. The Carrier Bag was designed first and foremost as a briefcase while the Musette was designed as a large all-purpose handbag. As for colors, Coach has made many shades of brown just as they've made many shades of British Tan. Colors can also change over time and some darker vcolors especially black fade noticeably with use and exposure to light and pollutants. They've also used leather from different sources and it's very possible that leathers on different bags won't be the same. You can't ever compare a bag to a different style or a bag made in a different time period. Remember, using a bag often WILL make the leather less stiff - you said yourself that this bag seems almost unused while your old Musettes have been used often, so doesn't that extra use mean less stiff leather?
As we've said many times before, you can only compare apples with apples, and those apples have to be from the same plant, month and year for any comparison to be valid. A Carrier Bag from 1989 is NOT going to have the same details as a Musette from maybe 10 years earlier. A briefcase won't have the same design features as a handbag.
BTW, I looked at the bag in the auction listing when you first posted and didn't see any problems.