This is an ESD isolated case for a 12/24 volt relay board commonly found on Amazon/other sites. Here's the exact relay boards I used:
12 volt: https://www.amazon.com/dp/B00LW2GM84?psc=1&ref=ppx_yo2ov_dt_b_product_details
24 volt: https://www.amazon.com/dp/B00LW2G7V6?psc=1&ref=ppx_yo2ov_dt_b_product_details
The author marked this model as their own original creation.