Crystal shelf clock with problem (Sunnyvale near Fremont H.S.)

Approx. 4 x 5 inches in size. Perfectly clear and heavy crystal (looks odd because I had laid it on the carpet). Even after changing the battery, the clock is very slow. I went online to find a replacement clock insert, but could only find round ones! The clock obviously comes out, so maybe someone would like to create new art out of the crystal part? Or challenge themselves to repair the clock?