The New York Mercantile Exchange might be shaking up its executive team, but it is still on track to complete an IPO next month.

The commodities and futures exchange plans to kick off a road show on Halloween to talk up the initial public offering, according to a source familiar with the matter. Shares could list on the

New York Stock Exchange

by the fourth week of November.

But things took a confusing turn late Tuesday when Nymex Holdings, the parent company of the Nymex, announced that its CFO had resigned from the 132-year-old commodities exchange -- just seven months after taking the job. The exchange says Jerome Bailey, 54, will continue on in an advisory role to the exchange through its IPO.

Bailey, a former

Marsh & McClennan

(MMC) - Get Report

executive, became the Nymex's chief financial officer and chief operating officer in March, after replacing Kenneth Shifrin, the acting CFO at the time.

But in an odd twist, Shifrin, currently Nymex's senior vice president of finance, is getting his old job back, succeeding Bailey as CFO.

Nymex had little to say about the

strange turn of events in the press release announcing Bailey's resignation. A Nymex spokeswoman says that no date has been set yet for the IPO and would not comment further on why Bailey abruptly resigned as CFO. She also wouldn't confirm the date the road show will begin.

It's unusual for a top executive of a company to step down on the eve of an IPO. A high-level corporate shake-up is the kind of event that can rattle the nerves of would be investors. In leaving the Nymex before it sells shares, Bailey is forgoing the possibility of a cashing in his chips.

Observers say it is not surprising that there have been changes to Nymex's executive team, despite the close proximity to its planned IPO, which is expected right before Thanksgiving. It is known to have a

clubby atmosphere and that's a big reason why the exchange, which specializes in trading energy futures and metals, has been slow to embrace electronic trading, even as its direct competitor -- the Atlanta-based

Intercontinental Exchange

(ICE) - Get Report

-- forges ahead with electronic trading.

"There was no financial disagreements with him," says a Nymex member familiar with the matter. When he got brought on as a CFO, Bailey also took on the vacant role of COO. But the Nymex member said the two jobs proved to be too much.

"We thought that his learning curve would be shorter, and it was not," according to a member familiar with the matter. Bailey could not be reached for comment.

Nymex shareholders have already voted in favor of the IPO, in which shares were priced in a range between $48 and $52 a share. The exchange had previously said it expects the IPO to raise $250 million.