Is this a good idea for a 5th month anniversary gift for my boyfriend?

This is a wonderful idea. Not only is it meaningful, it has significant and sentimental value in your relationship.

Every man is different - don't pay attention to Santa Paws. Generalizing men because of a certain experience, or stereotype is like saying all women enjoy douchebags for a boyfriend (which is far from the truth).

I gave my boyfriend a necklace just like you are planning to do, and he's been wearing it everyday for the past 11 months so far. He doesn't care what other people think about what he has around his neck because every time he looks at it, it reminds him how much we both value equality in our relationship and how devoted we are to make everyday count. It reminds him where we'll be headed and how our relationship becomes better as days pass.The necklace has sentimental value in our relationship - I'm actually going to get a copy for myself so I'm reminded constantly - and to reject something so wonderful, meaning and UNFORGETFUL shows how little said person will care about you in the future. Always cherish your relationship, your partner and the little things you see.

Be happy. Be healthy, and love with all your heart when you know it's right. :)

Sure, that's very thoughtful. Another idea would be a keyring with a little LED flashlight on it.