A brown solid at STP, with a melting point in the range of 153 - 155 C.
Synonyms: 3,4-dihydroxybenzenecarbonal, protocatechuic aldehyde, rancinamycin IV 
Molecular formula: C7 H6 O3
CAS No: 139-85-5 

Known to be produced by the bacteria Streptomyces lincolnensis "in a sulfur-depleted culture medium". (J Antibiot (Tokyo) 1976 Aug;29(8):777-86)

Also a common precursor seen in texts like pihkal on the synthesis of psychoactive chemicals.