IWC had a history of providing watches to specific army requirements to various countries of this world. The Mark XI is one of those famous models in this category. And we normally know them for their characteristic black dial with specific army layout and markings.
One odd deviation in this series of watches are the white dialled versions of the Mark XI that were delivered to the British Ministry of Defense. The one you see enclosed bears the markings 6B/346, 1657/48. Movement number (important as you will read further down): 1'148'818
Various theories are going around on why there are a few out there with this white dial. The theories go from "pre-procurement tests" to "acceptance tests" to "white dials for ground crew" to "white dials for officers" to "surplus stock sold without dials, purchaser made own (white) dials". I am sure there are even more theories.
Assessing common facts on those few white dial Marx XI that have surfaced so far show the following:
- they are all from the earliest production batches
- they all lack the Incabloc protection (see second picture below)
The movement numbering books of IWC show that movement serial numbers 1'148'801-1'150'000 and 1'162'001-1'163'200 were calibre 89 movements without Incabloc protection. All later produced calibre 89, coming off the production line after these first 2400 were having Incabloc shock protection.
It is believed, that the watches without Incabloc came frequently back broken to be serviced which is why, at some point in time - the dials were removed in order to clearly avoid mixing them up with Incabloc protected Mark XI's. When at some point the army decommissioned the Mark XI those that were without dial received "after-market" dials, some of them white.
Whatever the "truth" may be, this is the nice thing about collecting vintage watches: the history, the mysteries, the stories, the theories.