[Tudortomnz]

The Model A ''small bores'' were specific to countries that had horse power taxes on private vehicles. This was mainly Britain, France & some other European countries.
Australia , New Zealand & Sth Africa had no added tax on engine size, so no small bores. But, from 1932 Ford UK started to sell vehicles here as they were lobbying for preferential market access in British Dominions ; the small bore B4 became available in small numbers.
Little known was that Ford Canada offered the small bore option & they were sold in Singapore in the Model A era which may have had HP tax. It is likely they used the English produced engine as there was a production connection between Ford Canada & Ford Britain.

AF stamped blocks are not small bore specific. These are known on some Model A sold in Sth America which are US produced RHD cars with the standard size engine.
AF can be any part of a Model A vehicle sold outside the US.