Is that the only way to identify them? I ask because there is the 998 that looks like a 904 and some of them (but not all) have lockup and they all have the heavy duty components (4 pinion planetaries, 4 disc drums) like a 999 but they don't have the low first gear. Their in between a 904 and 999 if you will. I don't know how to tell them apart on the outside nor do I have any numbers for them to identify them, just when I get them apart I know how to verify the low first gear set.