The difference between aluminum sheets 1050 H14 and 1100 H14 is mainly the difference in aluminum content.
The aluminum content of 1050 H14 must be above 99.5% for 5261, and the aluminum content for 1100 H14 must be above 99.0%. The higher the purity of the aluminum sheet, the lower the hardness. 1100 is harder than 1050 in physical properties. Because 1100 has more copper and magnesium than 1050 in content, the hardness is better than 1050.