Nun-Dar. Who has it, and how does it work?

In this thread about the nun reality show ThelmaLou said she had “good nun-dar.”

A friend of mine was raised Catholic and she also has it. Here’s how good she is. My mother had a friend who became a nun, and was a nun for some years, and then left her order and eventually got married to a live man. When I was a kid we visited her a lot. Both before & after her marriage, which didn’t happen for something like ten years after she left the convent. Maybe 15 years.

So my friend who went to Catholic schools all her life and I were going through a bunch of old pictures my mom had sent. Here we are at the Grand Canyon, here we are in Santa Fe, and here’s my mom and her friend–

My friend said, “Ooh. Was she a nun?”

Me (mystified) “Yeah, I think she was at one time. But, uh, that’s her husband in the background…”

Friend: “You can always tell.”

I sure couldn’t. I asked her how she could tell–from a decades-old black and white Brownie snapshot. Friend: “Well, it’s easier in person but…I don’t know…you can just tell.”

So what are the clues? To me she and my mother both looked like unfashionably frumpy 60s housewives, or maybe schoolteachers.

wimple marks and sensible shoes.