Thumb J-300 Jumbo – Natural, Lawsuit era, 1980

Thumb J-300 is a Japanese acoustic guitar, manufactured in 1980 at the Terada Gakki factory. The instrument is based on a Jumbo body shape. Visually and structurally, this model refers to the Gibson J-180 specification, characterized by symmetrical double pickguards on the top plate and star-shaped fingerboard inlays. The guitar features a spruce top and maple back and sides. After our service work, which included fingerboard leveling, refretting, and crafting bone nuts, the instrument is ready to play.

Technical specification

• Manufacturer: Thumb
• Model: J-300
• Year of production: 1980
• Body: Spruce (Top) / Maple (Back & Sides)
• Neck: Mahogany
• Fingerboard: Rosewood
• Frets: Medium Jumbo (Condition: 100% – new)
• Pickups: None
• Electronics: None
• Visual condition: Very good (details in description)
• Finish: Natural
• Weight: 2.30 kg / 5.07 lbs

Body and construction The Jumbo-shaped soundbox features a top plate made of spruce. The back and sides are made of maple laminate, factory-dyed to a darker shade. The instrument is finished with a clear lacquer (Natural). A standard glued neck construction (Set-Neck) is applied. The double pickguards glued to the top modify the stiffness of the plate. In our workshop, the lacquer coating went through a cleaning and polishing process.

Neck and ergonomics The mahogany neck features a profile similar to a "C" shape. The neck is paired with a rosewood fingerboard, featuring star-shaped inlays. The nut width is 43 mm. As part of the service work, the old frets were removed, the fingerboard was leveled, and brand new Medium Jumbo size frets were installed. A new nut made of natural bone was also fitted. The fingerboard surface was cleaned and conditioned.

Sound The instrument is a fully acoustic guitar with no electronic circuit.

• Characteristics: The combination of maple back and sides with double pickguards stiffening the top results in a shorter sustain and a compressed, bright attack in the mid and high frequencies.
• Dynamics: The instrument responds quickly to the strength of the pick attack, offering a defined separation of sounds, which works well during strong rhythmic playing.

Additional information

The Thumb brand was an internal product line (house brand) of the Terada Gakki factory, intended exclusively for distribution in the Japanese Domestic Market.

The use of large, double pickguards (modeled on the "Everly Brothers" design), in addition to its visual function, physically dampens part of the top plate resonance, purposely reducing boominess in the lower registers.

Crafting components from natural bone (nut and saddle) optimizes the transfer of vibrations from the strings to the soundbox compared to standard synthetics of that era.

The service work we performed included: fingerboard leveling, complete refretting, crafting a bone nut and saddle, and setting the string action.

Hardware

• Bridge: Rosewood – the bridge features a custom-made saddle crafted from natural bone in our workshop.
• Tuners: Closed-gear mechanisms in a 3+3 layout. The chrome hardware went through a cleaning process and retains its mechanical efficiency.

Instrument condition

• Technical condition: The instrument is mechanically functional after a luthier verification. The truss rod works properly, and the frets are brand new.
• Visual condition: The guitar is preserved in very good visual condition. Minor dings and scratches appropriate for over 40 years of use are visible on the lacquer coating. The instrument has no structural wood cracks.
• Setup and Modifications: Complete refretting (Medium Jumbo), crafting of bone nuts, fingerboard leveling, and a setup of the string action for a new set of strings were performed.

Why choose this instrument

• J-180 Specification: A less common layout with double pickguards and star-shaped inlays.
• Maple body: The use of maple on the back and sides provides a faster attack and greater sound separation compared to mahogany or rosewood.
• New frets and leveling: The complete fret replacement (Medium Jumbo) and fingerboard leveling eliminate the wear resulting from use and ensure proper intonation.
• Ready to play: After our service work, the guitar is fully prepared for regular playing without the need for luthier visits.