Samsung Mobile Display show a 2 inch transparent OLED display at the FPD International 2009.

At the FPD-International, a mirror is placed behind the display to show that the back side of the display also shows an image.

The pixel count and resolution of the Samsung's display are 176 x 220 (QCIF) and 141ppi, respectively. The luminance is 300cd/m2 for the top emission and 100cd/m2 for the bottom emission. The transmittance of the display is 30%.
Source:Tech-On