Aston Martin has taken a big step toward a long-rumored initial public offering: The company said that it has filed to list its shares on the London Stock Exchange. 

An IPO would be a logical next step for Aston, which has returned to profitability after a multiyear turnaround effort. It's likely to attract considerable attention from investors, given the sharp rise in rival Ferrari's (NYSE:RACE) shares over the last couple of years.

It's still not quite definite that Aston Martin will go public. The company has promised a final decision in the next few weeks and said that if it happens, it will probably happen by the end of the year. Here's what we know.

A red Aston Martin DBS Superleggera, a low-slung, front-engined high-performance coupe.

Aston Martin's newest model is the DBS Superleggera, a ferocious 715-horsepower coupe aimed squarely at Ferrari's 812 Superfast. Image source: Aston Martin Lagonda Ltd.

Why hasn't Aston Martin decided yet? 

It's officially undecided because the company's board of directors and shareholders haven't yet officially voted to proceed with the public offering. The company said that if it decides to proceed, it will publish a prospectus "on or around" Sept. 20. 

Why now?

Aston Martin has been around for more than 100 years, and for most of those years, it lost money. But now, under CEO Andy Palmer, it's solidly profitable. It's thus worth much more than its investors paid: Reuters reported that the company could go public at a valuation of around 5 billion British pounds ($6.38 billion). 

Given that it's possible that Brexit could put a damper on Aston Martin's valuation (though Palmer thinks it won't have a major effect on Aston's business), now seems like an ideal time for Aston's investors to take their gains. 

Simply put, the IPO, if it happens, will be a chance for some of Aston's current owners to cash out at a good valuation now that the company is solidly profitable. Aston Martin itself won't be raising any cash from the stock sale. 

Who are Aston Martin's owners?

Right now, Aston Martin's principal owners are an Italian private-equity fund, Investindustrial; a consortium led by Kuwaiti private-equity firm The Investment Dar (TID); and German automaker Daimler AG (NASDAQOTH:DDAIF), which owns a nonvoting stake of about 4.9%. 

TID was part of the group that bought Aston from Ford Motor Company (NYSE:F) in 2007 for 480 million British pounds. Investindustrial and Daimler acquired their stakes in 2013. 

Aston said in a statement that Daimler would continue to be a shareholder after the public offering. Beyond that, it's not yet clear who would be selling, and that makes it hard to know for sure what's happening. It's possible that some of Aston's owners have been exploring the possibility of selling their shares privately.

Today's announcement suggests to me that an IPO is now very likely. But Aston can't yet say so, because its board and shareholders haven't yet voted.

Palmer is shown seated, in suit and tie.

CEO Andy Palmer has put Aston Martin on a profit-growth path. Image source: Aston Martin Lagonda Ltd.

Are those investors cashing out entirely?

It's not yet clear. Aston Martin said that at least 25% of its shares will be offered, but we don't yet know which investors are selling or whether they're selling all or part of their stakes. 

Will U.S. investors be able to participate in Aston's IPO?

Not unless they're institutions (meaning mutual funds, pension funds, and the like). Aston said very clearly that its shares will only be offered to "qualified institutional buyers" (or QIBs) in the U.S.; they won't be registered for sale to any individuals, even those who qualify as sophisticated investors.

That said, it seems likely that there will be ways for U.S. investors to purchase shares of Aston Martin after the IPO. If so, we'll cover it here on fool.com.

Is Aston Martin a buy at a $6.38 billion valuation? 

Let's stick with British pounds for the moment. Aston's hoped-for valuation of 5 billion pounds is about 21.4 times its 2017 adjusted earnings before interest, taxes, depreciation, and amortization (adjusted EBITDA, where "adjusted" means "excluding one-time items").

Ferrari is a larger company -- its revenue was about 3.5 times Aston's last year -- and it's more profitable, but it's probably the closest comparison. Ferrari's current market cap is about 21.67 billion euros, or about 20.9 times its 2017 adjusted EBITDA. 

Both are expected to show incremental sales and profit growth over the next few years, assuming that global demand for high-end luxury-sports cars stays strong. I think that 5 billion pounds (or $6.38 billion) seems a bit rich for Aston Martin.

That's based on what we know now. The valuation might look more reasonable once we see the prospectus and hear Palmer's case for the company and its growth potential. It's also possible that Aston will go public at a lower valuation that makes a stronger case for investing.

Either way, if Aston Martin can get even close to Ferrari's operating margins over the next few years, it'll be worth a close look from investors -- and we'll give it a close look once we know more.

John Rosevear owns shares of Ford. The Motley Fool recommends Ford. The Motley Fool has a disclosure policy.