In reply to Robin Cowan.

Officially, the all-brown bezel insert was only offered on the solid gold GMT-Master and GMT-Master II watches. However, prior to Rolex tightening control of service replacement components, it was not uncommon for two-tone GMT owners to have their gold and brown inserts replaced with all-brown ones during routine servicing and repairs, or even at the retailers when the watches were purchased brand-new (similar to how you will often find ref. 16760 watches with both Pepsi and all-black inserts, despite the fact that the reference was only officially offered with the red/black Coke insert when it was sold brand-new).