"She's Sumpin' Else" seems indeed to be the A side - a quickie cover of the original by Mississippi bluesman Dennis "Long Man" Binder, on the tiny Cottonwood label out of Amarillo, Texas. Petty apparently had recorded it if he published it. Binder had earlier recorded with Ike Turner for Sun (unissued) and Modern, and in Chicago for United. Comment by annaloog:
Promo copy labels added ... note the 'compliments' sticker on the "She's Sumpin' Else" side, published by Norman Petty's Nor Va Jak Music.
Judging from the RCA matrix numbers, "She's Sumpin' Else" might have been the preferred side. I'm not certain what the stamped 'A', in place of the usual 'I', 'R' or 'H' for RCA pressings refers to.