Many typefaces designed with a pen on paper (especially those from the 20th century) were licensed by different foundries, and were later independently digitized by them. Some special characters such as @ or the euro sign, were independently added later. Those “alternate cuts” are different digital versions of basically the same typeface design. They often vary in character set, letter proportions and kerning. Some are published under different names.
Skia is a stylish sans serif face originally built as a showcase for Apple’s QuickDraw GX technology, and as such has variable weight and width axes. Like a multiple master font, users with the correct software could fine-tune weight and width using sliders in their applications.