By Pat Ciarrocchi

PHILADELPHIA (CBS) – For art lovers, Friday is a big day at the Barnes Foundation.

READ MORE: Exclusive: Sources Tell CBS3 Criminal Charges Expected In Fire, Building Collapse That Resulted In Death Of Philadelphia Fire Lt. Sean Williamson

The public will be invited to see two drawings by the master, Paul Cezanne, which have been hidden for nearly a century.

To the untrained eye, the drawings look like any artist’s first stab at a landscape.

But for two art conservators, Gwenanne Edwards and Samantha Sheesley, the sketches became a discovery that’s rocked the Barnes.

Since the beginning of the 20th century, art scholars and guests would walk through the Barnes’ galleries without realizing that there were two watercolors with a hidden treasure from Cezanne waiting to be discovered.

READ MORE: 2 Suspects Fatally Shot During Home Invasion In South Philadelphia, Police Say

The sketches were on the reverse side of the framed watercolors – only to be revealed when Gwenanne and Samantha took the pieces out of the frames and meticulously lifted a backing from the two works of art.

Gwenanne found the first sketch, and next to her, Samantha, who is from Allentown, found the second.

Dr. Barnes had purchased the watercolors for $100, and it’s believed he didn’t know what existed out of sight.

“With the first two that we did make the discovery, we had hoped we might be finding more, but no,” says the Barnes Foundation’s Barbara Buckley.

Or at least, not yet.

MORE NEWS: Officer Fires Gun During Struggle With Suspect Wanted For Stealing Car, Philadelphia Police Say

“Cezanne Uncovered” is open to the public starting Friday, April 10th through May 18th, 2015.