Signed top right: ‘Norris’. Titled and inscribed verso: ‘Mexico XII; Opening / July 1966 / list no. 376’. Label verso inscribed: ‘Mexico XII; Opening / 135.’ In fine condition. Inscribed in the artist’s studio notes: ‘Format lay-out same as above, / slightly narrowed bars because of proportions / of panel. Green-orange dominance in ‘X’ / triangles: top- lt green oxide; r. + l. gradation of gray; / bottom – burnt sienna.’