Ian Anderson

Anderson states in this interview that he uses a Brook 3/4 Scale Parlour guitar.

Anderson states on his official site that he used a Martin 0-45.

Anderson states that he used a Martin 016-NY guitar on his official site.

According to his official site, Anderson had a white Fender Stratocaster guitar.

Anderson states on his official site that he's owned a Gibson SG.

Ian Anderson can be seen throughout the 2005 Estival Jazz Festival Concert playing a very small, narrow bodied acoustic guitar that has a very impressive and remarkably full sound due to the fishman piezo-electric transducer (pickup) it has. A bit of searching turned up this bit of info from Ian himself posted at jtull.com under "Ians Instruments" -

During the eighties, I switched to guitars from Andrew Manson, an English >luthier, who works in Devon producing hand-made guitars for aficionados of >acoustic instruments. My instruments are based on traditional designs by the >Martin Company as well as on the ideas of Andy and myself, and we have >come up with modern variations on the theme, giving a compact guitar with >the resonance and playability associated previously with the big “jumbo” style >guitars favoured by Country artists. The sexy little parlour guitars are not at all >common in pop and rock music: indeed, I am probably one of the very few to >use them. The instrument currently on tour with me is the smallest ever! It is a >3/4 size parlour guitar based on a French design of 150 years ago. I sent >Andrew Manson the drawings and measurements and even he was surprised >at how well it played and sounded, especially fitted with one of the Fishman >transducer pick-ups which I have been using since the late eighties. (https://www.andymanson.com/parlour-guitars)