SecurityID  (Tag = 48, Type: char)

CUSIP or other alternate security identifier

Used in:

• Indication of Interest (6)
• Advertisement (7)
• Execution Report (8)
• New Order - Single (D)
• New Order - List (E)
• Order Cancel Request (F)
• Order Cancel/Replace Request (G)
• Allocation (J)
• Quote Request (R)
• Quote (S)