Googled with some related terms and found a StackOverflow page zebra printers - MIFARE classic card APDU authentication failure - Stack Overflow
Used P2=0x60 and it worked!!!
Now I need to know why 0x60 works.
The Omnikey and SDI card reader implement the mifare interface slightly differently and neither follow the pcsc specification exactly.
You'll need to visit the Identiv site and get the SDI programmers reference.
The 0x60 is the definition for KeyA, for KeyB it's 0x61