Florida ? Robbers in surgical masks pulled off a $4 million coin heist at knifepoint outside a coin dealers convention in Orlando, getting away with gold, silver and a rare 1843 set of currency once owned by President Tyler.

It was the second time in two years that the Florida United Numismatists’ annual coin show had been hit, and this year’s loss was much larger.

On Saturday, a Minnesota coin dealer’s employee was unloading an SUV outside a luxury hotel when a robber grabbed him from behind and held a knife to his throat, witnesses and the victim told authorities. Two other masked men grabbed a suitcase from the SUV.

Sheriff’s Deputy Carlos Padilla said the coins were extremely rare, which could make it difficult for a thief to sell them.

Last year, thieves stole about $450,000 worth of coins by breaking into cars, most of them while dealers ate in restaurants.