Blues records have been around for almost 100 years and in most cases blues means green when it comes to monetary value. In 1928 Paramount Records released “Mississippi Jail House Groan” by Rube Lacy. A copy is now worth up to $2,500.00. In 1937 Vocalion Records released “Milkcow’s Calf Blues” by the legendary Robert Johnson. A copy can get you $10,000.00 today.These both fall into a category known as “Pre-war Blues.” Blues records that came out prior to World War ll can be very valuable.