RomeoMike wrote:

Then you would know that periods always go inside quotation marks. :-)


Not always. If the quote is a single letter or number at the end of the
sentence, then the period goes outside of the quotation marks, as in:

Mark your choice in the box with an "X".
or,
Jessica is a "10".

While the general approach in the US is to put commas or periods inside the
quotation marks, the rest of the English speaking world tends to use a more
logical approach depending on context: If the comma or period is part of
the quotation, then the punctuation is placed inside the quotation marks.
If the comma or period is not part of the quotation, then it is placed
outside the quotation marks.

The lore is that the US approach to placement of the punctuation marks had
its origins with mechanical typesetting. If a comma, or more particularly
a period, was placed outside of the quotation marks, it was more exposed.
Being relatively small, the small punctuation marks tended to break off
during the printing run. They were more protected if placed inside the
quotation marks, hence the origin of the US practice.