Yes, it was iodine. My husband even remembers his mother doing this when he was a kid. He did not burn when she would do this.
I also remember my not-so-tannible mom making her baby oil a nice, light, orange tint from the cheap tincture of iodine. She always tanned nice when she did that!
PS: added edit
forgot to mention I started doing that myself, this year
I used coconut oil mixed 50/50 with vitamin E oil (a little 4 oz bottle found in the vitamin section of Walmart) with about 5-10 drops of the detoxified iodine.