Journalism Online, the high-profile, if vaguely named, startup with a plan to charge for news on the Internet, says it has signed with media companies representing 176 daily newspapers. But it won’t say which ones.

On Thursday, PaidContent’s Staci Kramer reported she has “good reason to believe” that one of the companies is her corporate parent, Guardian News and Media, which publishes The Guardian and The Observer in London. To that list, I can now add Journal Communications, publisher of The Milwaukee Journal Sentinel, which claims just under a million monthly visitors to its website.

I called up the Journal Sentinel on a tip, and Sharon Prill, senior vice president for interactive media, confirmed that they had signed a letter of intent with Journalism Online. “I think like any other publishing entity, we’re exploring paid models,” she told me. The Journal Sentinel has experience charging for news: Some of their Green Bay Packers coverage is behind a pay wall for $7 a month or $45 a year. Asked if the program, dubbed Packer Insider, has been successful, Prill said, “Successful, in that it generates a profit, yes. But in terms of growing that subscription base, it’s been challenging like everything else.”

Signing with Journalism Online doesn’t necessarily mean the Journal Sentinel will decide to charge for more of its website. “We’re in the due diligence stage,” Prill said. For now, it means they’ll receive consulting assistance and perhaps better technology for charging readers if they decide to go that route. And while every market is different, you can get a sense for the pitch they’re likely hearing in Milwaukee from the posts I wrote about Journalism Online in June. Steve Brill, a co-founder of the firm, argued that newspapers could aim to extract payment from at least 5 percent of their monthly online visitors, which would be 46,550 people for the Journal Sentinel.

Meanwhile, don’t expect Guardian News and Media to be raising any pay walls. Emily Bell, the company’s director of digital content, recently made her position on them clear: “They are a stupid idea in that they restrict audiences for largely replicable content.” The Guardian is instead considering a paid members’ club that could include exclusive events and other offers, and that could be why Journalism Online is involved.

Who else is among the firm’s early clientele? Not Dow Jones, McClatchy, or Tribune, which all said they weren’t on board last week. If you know of other companies that have signed with Journalism Online, feel free to drop me a line.