Different post offices in New South Wales used specially-allocated numeric cancel stamps between 1850 and 1904. Many collectors of Australian stamps collect these numeral cancels.
There are different types of numeral cancels found for sale in the stamp marketplace these days. Some of the numeral cancels showed the number inside concentric circles or ovals, while others had several lines extending in all directions from the number, making a sort of starburst. Other varieties exist, including cancel stamps with horizontal bars.
When browsing New South Wales numeric postmarked stamps and covers for sale, remember to check back often; this page is updated daily.