As I remarked on another forum, the arabic numeral dials were a variation available as part of the normal model inventory. They appeared on 168.004s, 167.005s and 168.005s and were shipped around the world.
While most dials for these cal 551 and 561 models were either pie pan with faceted markers or domed with faceted markers, arabic numeral dials could be ordered from stock. They are uncommon but not rare.
Cheers
Desmond
4,314 Omega listings are live on the eBay market and 362 collector listings on the WatchProSite marketplace.