Thanks Dan. I'm guessing the SX-M and the rudder are black because most of the 353rd ponys Iv seen have black or yellow rudders.
The black rudder was a squadron recognition marking. Each squadron had a different color rudder. This was standard practice in the 8th AF
350th FS was yellow-LH was squadron code
351st FS had no color on rudders YJ was squadron code
352nd had black rudders with SX as squadron code
All were part of the 353rd.