Still don't know which AS504 number prefixes explain which type of machine your drawing block is?  The Library Manager has been updated for 2006 to help you along with this problem. 

Open the Library Manager and highlight the AS504 directory, in the "Look In" area of the manager, C:\Program Files\PCAD2006\Layout\As504.  Now, right-click and hold to see a list showing what the first three digits of an AS504 equipment number translates into.