Historians once believed him to be an Italian named "Guglielmo Soleri" who worked in Majorca,[1] but has since been more confidently identified as probably of Catalan origin.
Majorcan documents identify him as "Guillermi Solerii", citizen of Majorca, master instrument-maker and mapmaker (bruixoler).
Both are "normal portolan" charts, covering usual range (Mediterranean, Black Sea, Atlantic coast), but contain some stylistic differences.
The first (1380) is considered quite typical of the Majorcan school, geared to geographical depiction, with plenty of illustrations and inland details (e.g. rivers, heraldic shields, mountain ranges).
[5] Guillem Soler's c. 1380 (Paris) chart gives probably the first depiction of the royal arms of England as quartered with the royal arms of France (representing the English claims to the French throne in the 14th century)[6] Guillem Soler is also the possible author of a third piece, a recently discovered fragment (21x31 cm) of a Catalan chart, covering only a portion of the west Mediterranean.