We use "...or so" after numbers to indicate an imprecise amount: "A dozen or so"; "Fifty or so"; a decade or so"; "half past ten or so"; ten miles or so".

We tend not to use it with dates; we prefer "1820 or thereabouts"; "in the 1820s".

If a number is not stated or understood, we use different constructions: "She likes greens and browns and colours like that"; "He would rather send a letter or card - some form of written record, anyway - than use the phone." "Our son will spend the summer playing football or cricket - you know, some kind of outdoor activity - rather than watching TV."