in this case it was traditional haftones. Meaning it's a semi-transparent, adhesive overly that you cut out and stick on the original art. You can replicate the effect in photoshop as well. I'm sure there's plenty of tutorials on youtube that can say it far better than I.
ha, that $20 price tag isn't around anymore. This is when I was a student and needed the spare change to eat...literally. Now I'm on my own with some freelance Marvel money. I can add potatoes to my rice and beans now.