In the US, it is common on business cards, letterheads and email signature blocks to list phone numbers as
(212) 321-7654 (tel)
(917) 654-3210 (cell)
(323) 999-8888 (fax)
Sometimes a period is added after tel, but rarely after fax and never after cell. Sometimes the first letter of the modifier is capitalized, but often not.
I have never seen mob in the US to define a cell phone and rarely see mobile in printed materials (although it is used often in speech).
In resumes (and other documents with headings) the number is sometimes preceded by the phone type, as in
Tel: (212) 987-6543
While there are some area codes (the first three numbers) that are reserved to cell phones, many area codes are used for land, cell, and fax, and people do not necessarily know which numbers are which, so marking is common.
If someone only uses a single line, land or mobile, the parenthetical is usually left off. There is a growing pattern in the US of giving up land lines and only using cells (especially among younger people). Such folks often simply list their number without referring to its type.