For a period of time, Monnier was the CEO of Heuer/ TAG Heuer before leaving and then buying Zodiac in 1990. At this time, TAG Heuer made no watches themselves, and outsourced production to Roventa Henex. My guess is that Monnier was able to buy the rights to the TAG Heuer 1000 (which TAG Heuer phased out in 1990) and likely the other designs too and had them made in the same place.