Bother - you see, I've even tripped myself up! The smaller Buchanan I have is only 420mm - i.e without doubt a Mandola.
But Tom (confusingly and annoyingly) calls this the 'tenor mandola', which it can't possibly be as it's an alto instrument*. Tenor Mandola means 'a mandola in the tenor range' - i.e. an Octave Mandolin. Never, Use, The, Term, Tenor. Mandola. Or. Octave Mandola.
Mindst you - how would it sound if I strung it Gg Dd Aa Ee, I wonder, and what sizes would I use....
*Furthermore the mandola is the senior and original member of the family and thus 'should never be insulted with an adjective' (Louis de Bernieres)