David Rysdahl wears Derek Cardigan Math Symbol eyeglasses in the FX series Fargo Season 5 (2023).

Exclusive vintage inspired eyeglasses brand Derek Cardigan features math symbol accents on the temples of frames, a division and multiply symbol on the front as can be seen in the images, and = symbol on the sides.

The glasses are not produced anymore and the exact model is unknown but a similar model is the Derek Cardigan 7003 as pictured on the left.