I think they are a minimum of 15 years old though I can't say for sure. Trying to remember exact dates I saw posters in bathrooms of gay bars while drunk at 4 a.m. is challenging.
I'm not sure if they would be considered NSFW by American standards or not, so I am employing a cut. (Are dude butts NSFW? We have ads with dude butts at tram stops here but I haven't been in America for ages.)
Again if they are not old enough or offend anyone feel free to kill this post. I just thought it was interesting in context.