Hand numbered are the earlier of the forged style. Later they are stamped.
Sean, something got mixed in the chat. Grooves have always been there, only later in the 00s iirc around the time ISIS came out where the grooves removed, not the main front groove became much deeper.
You can see here the 1998 LPs and if you look at the DH there is eventually what the LP started to look a bit like iirc.
This thread needs pictures, but I always seem to answer on my phone.
Scan this big thread though
viewtopic.php?f=7&t=74449