In 1971, Heuer were selling into 96 countries worldwide, although the majority of sales were into North America and Western Europe.

The breakdown is as follows:

US & Canada: 1970 43%, 1971 35%
Western Europe: 1970 28%, 1971 33%
Domestic: 1970 11%, 1971 14%
ROW: 1970 18%, 1971 18%

So Japan was only 1 of 70-80 odd countries making up 18% of Heuer sales. At this point they weren't particularly selective about which market got what - this would come along more in the late '70s, with certain models only being available in certain markets. For me, that makes it very unlikely that "special" dials were being created for specific markets, particularly a market that wasn't in the top 10 of Heuer's markets by country. Even less likely that such a dial would be noticeably lower quality than contemporary Heuer dials.