Regional handwriting variation
Although people in many parts of the world share common alphabets and numeral systems (variations on the Roman alphabet are used throughout Europe, the Americas, Australia, and much of Africa; the Arabic numeral system is nearly universal), there are sometimes regional variations in how the characters are formed. These variations can be likened to a "regional accent" in handwriting.
There is often a great deal of variation within a given region, depending on the method of penmanship and teaching tools used. Some countries, such as France, have a national copybook. In other countries, such as the United States, the copybook taught at school is decided at the school district level. With greater communication and travel between various regions in modern times, many individuals are exposed to writing from other regions, resulting in greater interchangeability of writing samples between regions.
1 - In China and parts of Europe, it is written with a line at the top extending downward and to the left, as seen in serif typefaces such as Times Roman. It is sometimes - but less frequently - written with horizontal serifs at the base; without them it can resemble the common North American 7. In North America, it is usually written as a plain vertical line.
7 - In China is is commonly written with a serif descending from the top horizontal, and no crossbar through the middle. In North America is it usually written with just two strokes, the top horizontal and the (usualy angled) vertical. Schools run by the Roman Catholic Church have traditionally taught that a short horizontal bar should cross the vertical in the middle. It is not crossed this way in Japan.
9 - In parts of Europe, it is written with the vertical ending in a hook at the bottom. This version resembles how the lowercase letter g is commonly written. In North America and elsewhere, the usual shape is to draw the vertical straight to the baseline.
Z - In North America and China it is usually written with three strokes. In parts of Europe it is commonly written with a short horizontal crossbar added through the middle. This version is sometimes preferred in mathematics in other regions, to help distinguish it from the numeral 2.