What is this Screen Printing technique and how can I achieve it?

Hi guys,

I have done multiple Halftones in my career but I have never seen that kind of Screen Print? It is done to create a shadow in the Sign. I am wondering what process was used to get to this pattern, looking from the front it looked like a Bevel in Photoshop with noise added to the pattern or some kind of clouds rendering with effects added but I can't seem to figure out how to do it.

I figure someone might've done something similar on here.

Here's the link to the Image: https://postimg.org/image/ufpf2fymn/

Notice that they used mixed patterns for both sides of the shading.

Thanks,

Squantcher