It's no secret that Barclays (BCS) and its London parent made out like bandits when the bank purchased the U.S. operations of then-imploding Lehman Brothers. Now, there are reports that the bank is shopping for a U.S. retail banking operation with a market cap in the $10 billion-$30 billion range.

So which banks are the most likely takeover targets?

There are plenty: PNC Financial Services Group (PNC), US Bancorp  (USB), SunTrust Banks, Inc. (STI), and Fifth Third Bancorp (FITB) spring immediately to mind. But some of these banks are themselves distressed, although not as badly off as Lehman was back in the day.

SunTrust's market cap is $13.47 billion, and it has hit a new 52-week high today, at $27.21. But the stock's book value is over $35/share, and that difference may well be enough to send Barclays to look elsewhere. Like at Fifth Third, which is also touched a new 52-week high at over $13/share. Unlike SunTrust, Fifth Third's share price now exceeds its book value of about $12.44/share. PNC's shares are also moving up to within range of their 52-week high, and the bank's book value is below its share price.

• Financial firms make up three of the Dow’s top performers since 3/9/09

The best of the bunch is US Bancorp. It's book value is about $12.79/share, and its stock is trading today at nearly double that. Its market cap of more than $45 billion may also make it too rich for Barclays.

If Barclays is indeed shopping for a US retail bank, it is looking for deposits it can add to its paltry $3 billion-$5 billion US deposit base. That base must offset the bank's US commercial lending, or it will have to pay a wholesale funding levy to the US government. Adding a retail franchise with a large deposit base and good prospects for more earnings gives Barclays the deposits it needs to ward off paying a levy and enough earnings to help rebuild its capital through retained earnings.

Another interesting note to Barclays recon mission is that it might indicate that it believes that US financial reform, if it happens, will not include the so-called Volcker rule, which would force banks to keep commercial and investment banking operations separate. At the very least, though, Barclays expects new capital requirements and figures that the best way to raise capital is to buy another bank.

A more cautious approach may be that taken by the Royal Bank of Canada, which is waiting to see how US regulations before acquiring any US banks. But it looks like the shopping period is open, and it's not unreasonable to think that US banks with up to $50 billion in deposits may be attractive acquisitions for larger banks.

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