When you screw the cabinets to the wall it will suck the drywall in tight. You might have strips of drywall with thin layer of plaster over that. When drywall was introduced around 1951 it had perforated holes and was plastered over. This system only lasted for a couple years. I have some good pictures of a bungelow that we added a new kitchen, and converted old, galley kitchen into a butlers pantry. I would love to help with any questions or problems you might have. We have been a remodeler-contractor in Kansas City for 3 generations. Visit kevin_frye | overland park, KS 66207
our contact information is on there.