@MontereyJack,
MontereyJack wrote:
Yeah, periods are definitely the common American usage. I can recall first not seeing it in Brit books and thinking it must be a typo.
These things are style issues. Oxford Dictionaries says that in neither British nor US English is punctuating abbreviations made of initial letters mandatory, so you can have UK, BBC, NBC, NATO etc however in the USA it is a common alternative style to use periods for certain ones notably U.S. and U.S.A.
For abbreviations made of the first and last letters of a word, such Mr, Dr, Jr, Sr, Fr, St, the US, but not the British, practice is to use a period.
From looking at some American style guides, I see that Americans put periods after Messrs, Rev, Hon, (some do after PhD, BA, MA etc, some don't), and after middle initials such as in John C Smith.
In general, British style has been to omit them all, this has come about in the last 50 or 60 years I would say.
I have noticed that Americans often put a dash between letters and numbers, e.g. the B-1 bomber, the K-9 Corps, DC-9 aircraft, I-95 highway, 4-F army classification, in British English we don't. The TV series 'MI6' (a drama about the UK secret intelligence service) became 'MI-6' for US viewers.
I notice that I habitually write or type e.g. and i.e. rather than eg and ie.