On the other hand, if attire is taken from a specific era, it makes sense to denote it as such. Steampunk; however, as a term, could easily apply to the century, or even two prior to the 1800s, because it is science fiction written about technology that appears a bit early for it's time, and frankly, steam engines were invented by Archemedes in Greece around 260 BC. They just didn't have good enough metallurgy and gas law knowledge to build a sufficiently strong boiler to or pistons to make full use of it yet. In the age of powerful iron Cannons; however, they could have very easily brought about the full power of steam as early as say, the American and/or French Revolutions, also referred to as the Georgian Era. As such I make no apology for referring to Georgian Attire, if used in a steampunk setting and mixed with Steampunk accoutrement, as being a definite form of "Steampunk Fashion". This is especially true when using Steampunk fictional works, albeit my own, as the basis for it's original design and for it's very Steampunk drama related usage.
Besides, some elements of that clothing style continued in men's formal wear and in military Uniforms, especially Naval Uniforms of High Ranking Officers well into the early years of the Victorian Era. This is not surprising as formal Victorian Attire has been worn, in non Steampunk settings, in my own lifetime now. I know as I wore it!
My formal black tie level Army Officer Uniform, when I served in a Cavalry Division, was almost an direct copy of the American Cavalry Officer Uniform from the end of the Civil war, with the one exception that the hat is a replica of Naval Officer attire and the rest of the jacket trousers etc were clearly from the Cavalry. (As I modified that outfit specifically for the purpose of using it as an Admiral's Uniform from the Victorian era, this change of hats was convenient for me.) I cannot say if non-cavalry Units use the same black tie uniform or not as that is only division I served in. I also have seen wealthy men married or simply attending formal dinners in ties and tails within my own lifetime, although the tuxedo styles have certainly changed since then. I also have fashion history books that show clothing very similar to what Ben Franklin and George Washington wore demonstrated as wealthy attire for Gentlemen around 1810. As such, it is important that people recognize that styles of dress were not uniform thought the era and certainly not in all parts of the world during that era. I will discuss and demonstrate a little of what I mean about Georgian Steampunk attire below.
I have heard the time period prior to the Victorian era referred to as the Renaissance Era, but at least in terms of fashions, this must be broken down much further at least into several different centuries rather than including everything from 1500s forward until the Age of Enlightenment. We specialize in Naval costumes from a variety of centuries, but when I looked up the technical terms in "History of Fashion", the time period between 1600 AD to 1900 includes first Baroque, then the age of enlightenment, and finally the "Revolutionary Period" when sympathizers with the French revolution everywhere began adopting bicorn hats, instead of tricorn, or turning their tricorn hat backwards so as to avoid being confused with the rich guys headed to the guillotine. They also changed many other clothing styles including a great increase in striped pants.
This time period, the 100 years prior to the age of Queen Victoria, is also referred to simply as the Georgian Era, in honor of the several King Georges who came one after another during that century in England. Well, I guess that all of those time periods apply to some of what I most often prefer as I wear things often associated with the "Golden Age of Piracy" mixed with very military naval attire from that general period. I just enjoy clothing more that doesn't look similar to something I could pull off the rack at my local thrift store and put together in an older style. Enlightenment era Through Georgian/Revolutionary Era clothing includes things like knee britches or in some time periods and areas "pantaloons (which I love for comfort, coolness in Texas, and ease to sew), which started going out of style around 1800 (though not completely for formal wear), thigh length elaborate vests, and a different style of coat.
As it is easy enough to find Victorian Steampunk, I don't need to say much about that, lovely as it is, but will include a photo of the Uniform (now modified) that I mentioned along with a couple of dapper gents and a lady in Victorian Steampunk Attire for contrast below. Victorian attire is not so difficult for males, if they aren't obsessive about details, as styles of formal attire have been maintained to some degree, but the ladies find Victorian clothing so challenging as to pretty much require a large budget or good sewing skills and a lot of time. Men's attire can be put together from a few thrift store trips plus appropriate jewelry, hat, and goggles, but women's attire is far more difficult. As a result they often wear more Victorian undergarments, without the large, complex, and bulky skirts, especially hoop skirts, and just anyone to question why they are attending Steampunk events in what might be considered alluring, but terribly scandalous in the Victorian times. Frankly, I rather like it, and I wouldn't wear one of those gigantic bulky skirts in a Texas summer either even if I was in any way inclined to the wearing of women's clothing, which I'm generally not. (Of course it is very pretty women's clothing, so I might be persuaded sometime, at least for a laugh, and I'm quite sure I would look far less elegant and far more funny, than the lovely ladies we go around with in a formal Victorian Evening gown!)