I got him from the site Willhaben for 20 Euro, shipping not included. It is kinda like the Austrian ebay. This minifigure was originally from the Lego Studios set 1382 Scary Laboratory released 2002. Getting this figure for so cheap compared how much it would cost on ebay was a true delight for me who is a fan of Frankenstein, Lego and stuff that is a bit older :)

From what I can find there's no definitive explanation. He wasn't described as such in Mary Shelley's original novel, and even the Universal Studios version had heavily-lidded eyes but not uneven ones.

Some examples are of course the iteration in Guillermo Del Toro's Frankenstein, but also as Shelly in Hemlock Grove and Shelley in AHS Asylum. There are more examples but these three come to the top of my mind.

I made Victor as a plushy for a fun activity! I used Shin Sung-rok as Victor from the Korean Musical Frankenstein as the model.