There were two patterns of RACD, 'home service' frock. The first had 5-buttons and no outer pockets. The later pattern had 7-buttons (the same as the tunic) and inset pockets with rectangular flaps in the skirt. I do not know the exact date that the changeover took place, but it seems to have been in the late 1890s. As usual when changes of this kind took place, there was a transitional period when the old pattern was 'wasted out' and both styles could be seen worn within the same unit. I hope that helps a little, albeit belatedly.
More rarely seen is a 6-button upper garment that is often observed worn by bandsmen, usually with a trefoil cuff decoration in white and gold, depending upon rank. As this is different to the authorised full dress tunic, I can only assume that it falls under the description of frock, although I know not its precise details.