Cooley stands to reap at least $1.8m (£1.5m) in legal fees and expenses for its work on the initial public offering (IPO) of of Snap, the parent company of photo-sharing and ephemeral messaging service Snapchat, according to a securities filing.

Shares of Snap surged in their market debut this week, with the listing valuing the company at $33bn (£27bn).

Snap, which was founded in 2011, is a longstanding client of Cooley and Palo Alto corporate and securities partner Eric Jensen. Jensen did not return a request for comment about the firm's work on behalf of Snap, nor did Cooley's global capital markets co-head David Peinsipp, who is also working on the float with partner Seth Gottlieb.

Cooley's early involvement for Snap was revealed in a 2013 suit filed by former Stanford University student Frank 'Reggie' Brown IV, who claimed that Spiegel and fellow Snap co-founder Bobby Murphy had cut him out of Snapchat, which shortened its name last year.

Brown alleged in court filings that the duo sent him a "threatening" letter from Cooley's Jensen.

The dispute settled confidentially in 2014, but in securities filings last month Snap revealed that it paid $158m (£129m) to Brown.

Quinn Emanuel Urquhart & Sullivan, which once advised plaintiffs bringing similar claims against the founder of Facebook, represented Snap in the litigation, while Cravath Swaine & Moore and Lee Tran & Liang took the lead for Brown.

Cooley also owns a sizeable slice of Snap stock. Snap's IPO prospectus notes that GC&H Investments LLC – an investment entity formed by Cooley partners and associates – owns "239,800 shares of our Class A common stock and 239,800 shares of our preferred stock", the latter of which will be converted into the same amount of "Class B common stock on the closing of this offering". With Snap's stock price closing on Thursday at $24.48 (£20), the value of Cooley's shares is now roughly $11.7m (£9.5m).

The IPO immediately makes a billionaire of Snap's Spiegel, a son of Munger Tolles & Olson partner John Spiegel in Los Angeles and Melissa Thomas, the youngest woman to ever graduate from Harvard Law School and a former tax lawyer at a predecessor firm of Pillsbury Winthrop Shaw Pittman.

In securities filings, Snap notes that Munger Tolles has received $649,314 (£530,000) in legal fees from the company during the past three years. Former Hogan Lovells partner Christopher Handman, hired by Snap as its general counsel in 2014, receives a base salary of $475,000 (£388,000) from the company.

Goodwin Procter is advising underwriters on Snap's IPO led by Allen & Co, Barclays, Credit Suisse, Deutsche Bank, JPMorgan Chase & Co, Morgan Stanley & Co and Goldman Sachs. Underwriters' counsel on IPOs are usually paid separately by the banks, which are well compensated for their roles handling the largest public listings.