TC Yeo, a local fan of Japanese watches sent me photos of his vintage Citizen Auto Dater.
I’m not sure where he bought the watch but Citizen was pretty active in Singapore during the 60’s. I believe this Auto Dater dates back to the 60’s as well.
The shape of this watch reminds me of the discontinued rectangular Seiko SARA from the Mechanical line. Here’s a picture of the SARA013.