Quebec police are seeking the recovery of two ancient artefacts stolen from the Montreal Museum of Fine Arts last fall, with a  substantial reward offered.

Though the daytime theft of the two small antiquities took place in late October, police revealed news of the robbery this week and released security camera footage of the suspect.

Together, the value of the two pieces — an Assyrian bas-relief dating from fifth century B.C. and a marble head from the Roman Empire — is in the hundreds of thousands of dollars, though they are small enough that the thief was able to slip them into his pocket.

"They were very securely anchored or attached to their displays, and to some extent it's a mystery which has been under investigation by the [Quebec police] for the last couple of months," said Mark Dalrymple, an art theft investigator with Tyler & Company in London.

He added that selling the objects legitimately would be next to impossible, as museums, dealers and auction houses have been advised of the theft and images of the two pieces have circulated around the world.

The theft was not made public at the time it occurred to protect the police investigation, but the authorities chose to reveal it this week because investigators are stumped.

"We never give up hope. Sometimes I have recovered items a year, two years, three years, four years, five years down the line," said Dalrymple, a top art-world investigator who was also consulted after the theft of five tiny ivory sculptures from Toronto's Art Gallery of Ontario.

Along with the reward — an unspecified amount from the AXA Art insurance company, which is working with the Sureté du Québec — officials are offering an additional $10,000 to anyone who can identify the suspect caught on the museum's closed-circuit security video cameras.

The man seen in the footage strolling through the museum is about five foot seven inches in height and was wearing jeans, running shoes, a dark jacket and baseball cap.

According to the museum, the theft is an isolated incident. Items on display are protected by security systems that include motion detectors and guards patrolling the galleries.