Tintype portrait of a reserved man and woman (photograph)

Sixth plate tintype with typical darkening and moderate surface wear that obscures the image, slight bend to plate. Late 19th century, 3.5 x 2.5 inches. A man and a woman, siblings or a couple, not particularly warm. He's wearing a white bowtie, she's not very pleased, they're holding their own hands. Hopefully not a wedding portrait.