4TF Letter D serial number

[D RODZ]

What's up. I have a teammate that has the red 4 The Fallen that has the letter D next to the serial number. What does that mean?

 

[Youcallthemlogs]

Deez nutsssss

 

[KontrolledKaos2]

Deez nutsssss

Gottttt Eeemmmmmmmmm

 

[Sambo]

My buddy has a White OG DC that has that to. Demo maybe? Probably not but I have never seen it before.