The answer is on the cover of the 80s Live '68 LP: "This album was recorded on a mono Norelco cassette recorder using a hand held mike and a Norelco C-120 cassette."
Norelco was the US brand name for Philips products in the '60s. Philips invented cassette tapes. The first portable cassette recorders came out in 1963, and the first Norelco version, called the Carry-Corder '150', similar to the original Philips EL 3300, was presented to the United States in 1964. It looked like this:
