Alright so here we go, below you will find images from Captain marvel Adventures 30, 31, 32, 34. They all have what the original poster describes. They are all wartime comics (from 1943-44) and only have one staple. And, there are very few adds within the comic, most are concentrated  at the beginning and end. I guess books sold well enough back in the day that there was no need for extra revenue through ads. I have two copies of 30, so just in case there was any doubt to this being normal, you