I want to know the answer to the following question:
When did the 33 1/3 rpm hit the market?
All the background I'm provided with is that "After World War II, two new competing formats came onto the market and gradually replaced the standard "78": the 33 1⁄3 rpm (often just referred to as the 33 rpm), and the 45 rpm (see above).". Is that enough to answer the question?
Answer: no