Leslie speakers are usually associated with the Hammond organ. Don Leslie first created his speakers in 1941 and referred to them as Vibratones. The name reflects the unique audio effects the speakers produced because of a rotating baffle inside the speaker. The Leslie sound was prominent on many rhythm-and-blues and rock 'n' roll records. Guitarists such as Eric Clapton and Stevie Ray Vaughn plugged their guitars into Leslie speakers to achieve the Leslie effects. Dating Leslie speakers is relatively easy. The speakers have production codes stamped on them, as do the speaker cabinets. In addition, a number of other clues provide helpful information.
Examine the Leslie tag and other visual clues. Foil CBS tags indicate that the Leslie cabinet was built after 1966. Leslie cabinets built before 1966 have metal tags. A typewritten metal tag was used from the mid to late 1970s. Leslie introduced its new Leslie logo in 1975. Another visual clue is the material used to construct the baffles. The baffles in Leslie cabinets were constructed from hardwood prior to 1970. After that year, baffles were constructed from particle board.
Check to see if the speaker cabinet is a one-speed or two-speed model. If the speaker cabinet has only one speed, then it was built prior to 1963. Leslie introduced two speeds, fast and slow, in 1963 with the Model 125 Leslie.
Look for the production code on the speakers. After going through a variety of names, Don Leslie officially named his speakers Leslie speakers in 1946. Beginning in 1946, all Leslie speakers were stamped with a production code. The production code consists of six digits divided into three categories, XXXYWW. The first groups of digits is the company EIA code, the "Y" is the year of production, and the "WW" tells what week the speakers were manufactured.
Find the production code inside the Speaker Cabinet. Leslie began putting a production code inside the speaker cabinets in 1956. The production code is four digits, but it is sometimes hidden behind the bass speaker. The production code allows you to place the Leslie speaker cabinet with a time frame, although it doesn't provide an exact year of production. Leslie speakers cabinets built from 1951 to 1958 are marked 21H, and those built from1958 to 1963 are marked 22H. The codes 122, 142, 147 and 148 all indicate that the speaker cabinet was built after 1963.