Wang 1200
From Just Solve the File Format Problem
The Wang 1200 was Wang's earliest dedicated word processor, released in 1972. It used cassette storage. Later in the decade it was superseded first by the Wang 2200, then later the Wang OIS.
The cassette format stored each text line as a fixed-length 100-byte block. Lines were stored immediately after you finished typing them, which didn't provide a way to insert text into earlier parts of the document, unless you read the entire tape and edited as you transfered it to another tape (which required two tape drives). There was an option to store each text line twice in a row, to assist in document recovery in the case of a bad spot on the tape.
