Arranbee (R&B) doll clothing is untagged with the exception of the Nancy doll from the 1930s.  Arranbee made fabulous clothing which is not difficult to identify as original.  Arranbee used "bias" tape for the closures, and square snaps.  This was there practice, and fairly easy to spot.  Look at the closure of the dress, and you will see either bias tape in the same fabric as the dress, or a solid bias tape.  The snaps will be square.  If the seams on the garment are serged, and it has the bias and square snaps ........ it is likely Arranbee.  When in doubt, refer to the doll identification book by Suzanne DeMillar for photos of Arranbee clothing.  Happy Dolling!