Where is it from in SA? if you don't know then you might have trouble getting a correct ID.
IMO eyes colour means nothing with these two. Same goes for the trim on the tail.
You can go with the usual eye colour and tail shape crap but it's been proven wrong many times. People choose to go with this when many Panaque owners I know do not. the only real way to know is if you know where it was exported out of. This is not true for all of them because some 191's and 418's are easy to tell apart when others are not.
Really if you paid good money but not a crazy amount for a Panaque of this size and one that looks as healthy as it does you have nothing to worry about. Care us exactly the same for all of them.