This is a Original Size icon. We've made it in iOS style, first introduced in iOS version 7 and supported in all later releases up until now (at least iOS 11). This style is based on thin two-pixel lines and is optimized for 50x50 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 12,300 icons, all in the same style and quality.
The icon is a rounded horizontal rectangle. On this card is inscribed "1:1", as tall as two thirds of the rectangle's height, representing a zoom ratio indicative of the icon's original size. The icon represents setting the zoom level to the original level.