A state prisoner is charged with posing over the phone as a would-be buyer of a $14,000 Rolex watch and then arranging for an accomplice to rob the seller at a Peninsula shopping mall, a prosecutor said.

Defendant Jermaine Shermal Nelson, who is due in San Mateo County Superior Court on Monday, was serving a 16-year term for robbery at the California Men's Colony prison in San Luis Obispo when he made a cell phone call in response to a Craigslist's ad for the watch, officials said.

The seller, however, was in for a rude surprise. Instead of selling the pricey Daytona timepiece, he lost it and the one on his wrist to a gun-wielding robber.

Lamar Diante Cox, 37, is accused of being the holdup man and is also due in court Monday. He allegedly met the victim, who wasn't named, at Hillsdale Shopping Center in San Mateo on Aug. 20, 2011, ostensibly to buy the watch. The men even went to a jeweler at the mall to verify the watch's authenticity and value.

But when they took the victim's car to the bank so Cox could purportedly withdraw money for the purchase, the robber instead pulled out a gun. Cox allegedly took both the victim's Rolex watches, the Daytona offered on Craigslist and the $9,600 Submariner he wore, prosecutors said. The victim immediately reported the robbery.

Police say Nelson, 37, then arranged, from prison, for Cox to travel to Texas in order to sell the Submariner to a man in Houston. The Daytona was never recovered.

In September 2011, police posted an ad on Craigslist offering a Rolex for sale and got a call from Nelson. They arranged to meet, but Nelson called it off at the last minute, police said.

Nelson and Cox are charged with robbery and conspiracy to commit a crime. They are being held in lieu of $500,000 bail, Wagstaffe said.

Contact Joshua Melvin at 650-348-4335. Follow him at Twitter.com/melvinreport.