20 Leva Academy of Science

Issued in the final months of Todor Zhivkov's 45-year rule, this commemorative marks the 100th anniversary of the Bulgarian Academy of Sciences — founded in 1869, just eight years before Bulgaria regained autonomy from the Ottoman Empire. The Academy was established in Braila, Romania, by Bulgarian intellectuals in exile before relocating to Sofia.

The .500 fineness is notably low for a commemorative silver issue, a reflection of the chronic hard currency shortages plaguing the Bulgarian state in its last years under communist governance.