So I was chatting with Amy Chase (writer of Fixation, first issue currently available at your better comic shops, and at mine as well!) as I was ringing up her comic book purchase, when she pointed out the bagged copies of the Not Safe for Work cover of Gastronomique #2 that I had at the front counter. Why are they at the front counter? Because I’ve had problems with these particular types of variants…walking out the door without my knowledge, if you get my drift. Thus, I just keep them discreetly by the register, where the Normal Folks won’t pay attention but the Real Heads know what’s goin’ on.
Anyway, the reason Amy pointed out said bagged variant was to wonder aloud what the first “bagged adult variant” may have been. I mean, not the naughty comics, like Black Kiss (discussed here) where there was only one cover (oh, for those days again), but it was a bit rough for open display on the shelf, and the comic was polybagged with a card over that cover. She meant the comics where there were a handful of “all (appropriate) audiences” covers, along with one, or two, or five Not Safe for Work variants that were polybagged with boards or some other feature that hid the imagery.
I mentioned in that post I’ve already linked once that maybe the best known version of this particular publishing strategy was Sex Criminals where, say, issue #11 would have your wholesome cover suitable for Sunday schools:

…and you’d simultaneously have the Adults Only cover available in this opaque polybag:

…containing Godless filth distributed by Zdarsky and Fraction, Professional Pornographers.
Amy said that she thinks Sex Criminals was the first series to have a standard cover accompanied by a polybagged NSFW variant, which…I couldn’t dispute. At least, not without research (AKA Googling).
Sex Criminals #11 came out in 2015, and as far as I can tell, that was the first issue of the series to have the polybagged NSFW variants. (This is where I miss having access to Diamond Comics’ stock catalog, where I could look this up for sure.)
The first thing that came to mind was the 1989 Leather and Lace series, which came in a polybagged Adults Only version and a “general audiences” version (which I go into detail about here). But it’s not really the same thing, as these are, technically, two different comics: one with X-rated material and one with the X-rated material removed. Yeah, I know. The bagged adult edition did have slightly racier covers, but this wasn’t really the same thing as the Sex Criminals reg-vs.-NSFW covers, as in Leather and Lace‘s case, the adult comic is the main book, the “general” version is the weirdo variant. And oddly, I don’t think even the L&L adult covers featured any outright nudity.
Anyway, I thought about this question for a bit, dredging what’s left of my memory for any earlier examples of regular ol’ comics with bagged naughty variants. Ultimately, I turned to that aforementioned Googling, and turned up this:

Perg #6, published by Lightning Comics in 1994, came with a couple of Gold variants, both polybagged. One was just the same cover pictured here, just on a gold-foil paper. The nude gold polybagged edition had a similar but different image, this time with everyone in the altogether. (You can see all the covers here.)
This isn’t quite the same thing, as the polybag is clear and doesn’t hide the image (unless the included Certificate of Authenticity was put over the front of the cover). But so far this is the earliest comic that had a standard cover accompanied by a nude polybagged cover (obscured or not). But in terms of comics that had a Not Safe for That Workplace variant in an opaque bag, Amy may be correct that Sex Criminals was first out of the gate.
Now is the time where I’ll throw things out to crowdsourcing. Can you think of a comic with a main Safe for Work cover with a nude polybagged variant, either in a clear bag or not, that predates either of the comics above in either category? I promise not to call you a pervert if you have suggestions.
“Perg” is an incredible clash between a sexy cover and the unsexiest-sounding title for a comic book I’ve ever seen. It sounds like an ethnic slur for a country that no longer exists.
Was it supposed to be Perv, and they thought they were clever? “No one will buy our naughty comic if they know we’re calling them pervs. Let’s change a letter.” Either that, or maybe they forgot the correct term and thought it was “pergs”.
Dynamite were doing “risque” variants in the early 2010s of titles like Dejah Thoris. They definitely used partially obscured polybags for that series and Vampirella later on, but I don’t know when they started.
Maybe this list might help ya –
https://comicvine.gamespot.com/variant-cover-nude/4015-58143/issues-cover/