Can you find another example?
Roman Empire isn't really BM's setting. And it's the sole pre-modern case that I was aware of in general, too.
Writing in medieval times used lots of abbreviations, partly because much of what you need to write in things like books of prayers and church rolls are formulaic, but also because ink and parchment or vellum were extremely expensive.
You can find here a list of common medieval abbreviations, around half of which are not really abbreviations but acronyms:
http://www.newadvent.org/cathen/01022a.htm
