Delta new hires are all top notch regardless of background.
It's a pleasure to fly with new guys.

One fun game is guessing thieir background without asking.
A tried and true discriminator is the old airspeed trick or some variant.
When ATC says slow to 210 knots you just reach up and set 211 in the window.
You can usually tell by the FO's reaction whether he was Navy, Air Force or civilian. Sometimes you can even tell their rank.