& btdesignex()
 
  Syntax: btdesignex(<UnitRef>)

  This function returns '1' if the specified unit reference exists in 
  the /mechs directory and '0' if it does not. Note that if you copy a 
  template into the mechs directory, you may need to perform a 
  @restart before it becomes visible.
 
  Example:
 
  > think btdesignex(AS7-D)                                                         
  1
  > think btdesignex(AS20-C)
  0