In BrE, we are supposed to put the full stop after an abbreviation that does not end with the last letter of the word:
Prof. (Professor)
Rev. (Reverend)
When it ends with the last letter, we don't use a full stop:
Mr (Mister)
Dr (Doctor)
However, this rule is often broken/ignored in BrE. Indeed, it was only when I became a teacher that I learned of its existence- I went through school and university without knowing it. I follow it now, and it is easy to do so- simply look at the last letter and BrE pedants will approve of your choice. :-D