are this couple my great grandparents?

Can anyone please date the era of this photograph - a year ago or so my eldest cousin gave me custody of family photos, most of which were unmarked with names, places or dates. She wanted to handball them to someone who would keep them for future dscendants who may take an interest in their ancestors. Many of the subjects in photos with some information have now been confirmed by other family members in South Africa who I discovered after a telephone call made possible by an unusual surname on a postcard to an aunt of my mother's generation. This wedding photo may be my maternal great grandparents, who migrated from Scotland to South Africa soon after their marriage, worked on a timber plantation, then raised a family in Port Elizabeth, and many of their descendants remain there but as the family fragmented geographically they lost contact. I have been fortunate to establish regular email communication with a second cousin one generation removed and jointly we have made the jigsaw into a family tree, but we wish to attach photos to names wherever possible.
I understand clothes are an indicator of eras, so can anyone help me pinpoint this one for timeline please.