To get a 100% ID, wait till it's 4 inches or so when i'll get a orange adipose fin or not.
Apidose fin will change colour reguardless. Its dependant on wether or not the apidose fin matches the tail colour at that size. Colour match, its a tat, no colour match is armatus. Jaw/head structer will soon be enough to tell, slight upturned nose will mean tat, downwards nose armatus.