A new Securities and Exchange Commission filing from the company reveals that the buyout was the result of a process that began in February with a list of 24 potential acquirers that was subsequently winnowed down to 16 companies, then to five and finally to three.

“From February 25 to April 1, Palm management, Goldman Sachs and Qatalyst Partners were in contact with a total of 16 companies including HP,” Palm says in its Preliminary Merger Proxy. “Of these, six companies, including HP, entered into nondisclosure agreements and participated in meetings with Palm and its advisors to review non-public information concerning Palm regarding a strategic transaction.”

And of those six, three made formal acquisition proposals after Palm (PALM) determined that it preferred an outright sale to the intellectual property transaction that at least one of those companies had been leaning toward.

The two companies in addition to HP that presented acquisition proposals are referred to as Company A and Company B. A fourth company, referred to as Company C, had initially been in discussions with Palm regarding an intellectual property transaction and later made a proposal to acquire Palm….A fifth company, referred to as Company D, contacted Palm on March 18 to discuss an intellectual property transaction but did not make a proposal to acquire Palm. Company D did not enter into a nondisclosure agreement and did not review non-public information about Palm. Discussions with Company D continued intermittently until April 15.

So what are companies A, B, C and D? HTC, Lenovo, Dell (DELL) and Huawei, most likely, though there’s a chance that ZTE (Zhong Xing Telecommunication Equipment Company Limited), which was believed to be interested in Palm, could be one of the four as well.

Recall that HTC was rumored to have dropped out of the bidding for Palm in late April. At that point, speculation on potential acquirers focused on Lenovo, though already, some–ahem–were suggesting the more likely suitor was HP (HPQ).

Dell and Lenovo would have been interested in Palm for many of the same reasons as HP–a turnkey smartphone division with a robust, scalable operating system. And for telecommunications equipment suppliers Huawei and ZTE, the acquisition of Palm would have been a quick and easy way to leap into the smartphone market with a known brand and strong OS.

Anyway…ultimately the bidding war for Palm came down to a battle between HP and that mysterious Company C. HP’s first offer was for $4.75 a share in cash. A second company matched that bid, and a third proposed an all-stock deal. At this point Company C was interested only in an intellectual property deal.

After Palm balked at those $4.75 bids, the company that had proposed the all-stock-deal dropped out. And Company C suddenly circled back with an acquisition offer of $6 to $7 per share, evidently having determined that its need for Palm’s patent portfolio merited the acquistion price. That sounds to me like HTC, which is facing a nasty patent battle with Apple (AAPL), a battle in which Palm’s patents could have proven quite handy.

But C’s proposal included a $60 million kill fee and some other conditions Palm didn’t much care for. Then the company reduced its bid to $5.50 a share. At that point Palm approached HP and closed the deal.

On April 24 Palm’s CEO and advisors communicated to HP and its advisors that, to remain in the process, HP must improve its offer significantly and immediately. Later that day, HP’s financial advisors verbally delivered a proposal to acquire Palm for $5.70 per common share in cash. HP’s financial advisors also requested a five-day exclusivity period. On April 25 HP delivered a letter confirming this proposal with a target announcement date of close of business on April 27 and sent a draft exclusivity agreement covering such period on April 26.

“We put the NDA in place because the iPhone OS includes many Apple inventions and innovations that we would like to protect, so that others don’t steal our work,” Apple (AAPL) explained in a statement posted to its Developer Program site. “It has happened before. While we have filed for hundreds of patents on iPhone technology, the NDA added yet another level of protection. We put it in place as one more way to help protect the iPhone from being ripped off by others. However, the NDA has created too much of a burden on developers, authors and others interested in helping further the iPhone’s success, so we are dropping it for released software.”