On the one hand true gentleman are rare, and if you've found one hold onto him.
On the other hand, many are the men who can put on the gentlemanly air for the sake of wooing. Time alone will tell if he remains consistent, or if he is putting up one hell of an act, until he has you. If the latter is the case, expect things to change exponentially once he feels secure in the idea that you are his, as it were.
What you do is be observant of him. If his gentlemaniness is a facade, time and activity will reveal the holes in the armour.