I wonder if they bought these via online auctions, which probably had COAs and they accepted them.

http://www.bbc.co.uk/news/world-europe-43933530

A French museum dedicated to painter Étienne Terrus has discovered paintings it thought were by him were fakes.

The Terrus museum in Elne in the south of France discovered 82 works originally attributed to the artist were not painted by him.

More than half the collection is thought to be fake. The paintings cost about €160,000 (£140,000).

Staff at the museum were not aware of the forgeries until a visiting art historian alerted them.

The council in Elne bought the paintings, drawings and watercolours for the museum over a 20-year period.