The harps I have listed as 'gothic' (Wartburg through to Estense) date from between about 1350 to 1600. The Gothic form is depicted in paintings from before this date but no instruments survive earlier than the Wartburg. Characteristics of the gothic form is the double-peaked shape, with the neck having a 'peak' at the bass end and the treble end, both about the same time. I also have included some instruments where the bass end rises higher - this is really a baroque development but if the instrument has the treble end peak, and other gothic features, I allow it as gothic.
Gothic harps are typically diatonic, with gut strings, and buzzing bray pins, giving them a characteristically nasal and pungent timbre through their entire range, very different from modern harps. Two Italian examples have a second parallel rank of strings to provide chromatic notes but both are of the classic gothic form.
I am not aware of any other extant gothic harps but I will be happy to add any that are drawn to my attention.