PIN index is a safety measure for gas cylinders. What is the PIN index for nitrous oxide?

Pin Index safety system: To discourage incorrect cylinder attachments, a pin index safety system has been adopted by cylinder manufacturers. The relative positioning of the pins and holes is unique for each gas. Pin Index safety system for medical gas cylinders: Gas Index Pins Air 1 and 5 CO2 mix (CO2 <7%) 2 and 6 CO2 mix (CO2 >7%) 1 and 6 Cyclopropane 3 and 6 Ethylene 1 and 3 He-O2 (<80%) 2 and 4 He-O2 (>80%) 4 and 6 Nitrous oxide 3 and 5 Nitrogen 1 and 4 Oxygen 2 and 5 Ref: Morgan, Jr. G.E., Mikhail M.S., Murray M.J. (2006). Chapter 2. The Operating Room: Medical Gas Systems, Environmental Factors, & Electrical Safety. In G.E. Morgan, Jr., M.S. Mikhail, M.J. Murray (Eds), Clinical Anesthesiology, 4e.