Not to friends but we went to a nude spa once and it was a real turn on seeing other guys get hard for my wife
Lots of friends have seen my wife nude in photos, but only one guy saw her naked for real when she did a streak in the garden with his wife. Even then, I am not sure if he had good look at her. We watched them pulling down their swimming costumes and running away from us, but looked away from the full frontal view as they ran back towards us. She did a naked twirl for us afterwards which he might have seen. I have dared her to flash men friends, but she always refused. She said it would have been embarrassing for the guys. I took that to mean she wouldn't have minded otherwise. So the streak was the only time she's stripped off in front of a friend. I think the OPs story is amazing. In my youth, I had a girlfriend who got naked in front of friends a few times. This was usually without any encouragement from me and I didn't always appreciate it at the time.
Fortunately, big, clunky video recorders came into being in '81-'82. And got better after that. <grin>
I've showed my buddies nude pics of the wife on my phone with her there to watch us looking at them. She loved it
Only a few of my friends seen my wife nude or topless. That was float trips, party cove, or skinny dipping. and a couple of times when friends dropped by our place, and she just happened to be naked. I did give one of my friends a chance to engage in some foreplay and oral, because he had shared his woman with me, but he was too nervous to preform, so that didn't work out. She more or less chose, who she showed herself to. Male or female. She liked pushing other women buttons, to she what reaction, she could get out of them.
Since I'm 'talking the talk', I may as well 'walk the walk'. So here's a recent nipple for examination. Not bad for an older MILF, eh?