Can someone tell me what medium was used to create Pulp magazine covers, and share any information on techniques ?

I've been on a google journey that so far hasn't been able to help me. A Redditor posted a link to these drawings a little while ago and I've been unsuccessful on finding out how to recreate the style and how exactly they were made. Is anyone experienced illustrating in this style, or would be able to point me in the direction of someone who is? Thanks!