Condition is unknown, but at €340 this sits below the supplied €409 25th-percentile comparable and well under the €479 median, making it a strong deal if it is complete and working. It is not an ambitious ask; there is meaningful room for normal age-related servicing without immediately erasing the value.
The GF-777 is a desirable Japanese vintage boombox-style all-in-one, valued for its powerful, lively presentation, substantial build, and visual rarity rather than modern convenience. Its integrated amplifier, radio, cassette section, and battery operation make it a compelling collectible and usable system. Before buying, confirm that both channels, cassette transport, meters, controls, aerial, battery compartment, and mains operation work; missing covers or a dead cassette mechanism matter. At this price, though, a sound, complete example is a genuine buying opportunity.
Independent perspective — not a price guarantee. Always verify condition, accessories and provenance before purchase.