diff --git a/SabreTools.Serialization/Models/NES/Enums.cs b/SabreTools.Serialization/Models/NES/Enums.cs
index f3b568cc..7a823384 100644
--- a/SabreTools.Serialization/Models/NES/Enums.cs
+++ b/SabreTools.Serialization/Models/NES/Enums.cs
@@ -464,6 +464,7 @@ namespace SabreTools.Data.Models.NES
     /// <summary>
     /// Extended Console Type
     /// </summary>
+    /// <remarks>Actually only 4 bits (bits 0-3 of flag 13)</remarks>
     public enum ExtendedConsoleType : byte
     {
         /// <summary>
@@ -601,7 +602,7 @@ namespace SabreTools.Data.Models.NES
     /// <summary>
     /// Vs. Hardware Type
     /// </summary>
-    /// <remarks>Actually only 4 bits</remarks>
+    /// <remarks>Actually only 4 bits (bits 4-7 of flag 13)</remarks>
     public enum VsHardwareType : byte
     {
         /// <summary>
@@ -643,7 +644,7 @@ namespace SabreTools.Data.Models.NES
     /// <summary>
     /// Vs. System Type
     /// </summary>
-    /// <remarks>Actually only 4 bits</remarks>
+    /// <remarks>Actually only 4 bits (bits 0-3 of flag 13)</remarks>
     public enum VsSystemType : byte
     {
         /// <summary>
diff --git a/SabreTools.Serialization/Models/NES/Header1.cs b/SabreTools.Serialization/Models/NES/Header1.cs
index 90214065..84da3d73 100644
--- a/SabreTools.Serialization/Models/NES/Header1.cs
+++ b/SabreTools.Serialization/Models/NES/Header1.cs
@@ -58,7 +58,7 @@ namespace SabreTools.Data.Models.NES
         /// This byte is not part of the official specification, and relatively
         /// few emulators honor it.
         /// </remarks>
-        public byte ReservedBits23 { get; set; }
+        public byte Byte10ReservedBits23 { get; set; }
 
         /// <summary>
         /// PRG RAM ($6000-$7FFF) present
@@ -91,7 +91,7 @@ namespace SabreTools.Data.Models.NES
         /// This byte is not part of the official specification, and relatively
         /// few emulators honor it.
         /// </remarks>
-        public byte ReservedBits67 { get; set; }
+        public byte Byte10ReservedBits67 { get; set; }
 
         #endregion
 
diff --git a/SabreTools.Serialization/Models/NES/Header2.cs b/SabreTools.Serialization/Models/NES/Header2.cs
index 35d63ac2..c7d6b312 100644
--- a/SabreTools.Serialization/Models/NES/Header2.cs
+++ b/SabreTools.Serialization/Models/NES/Header2.cs
@@ -101,14 +101,66 @@ namespace SabreTools.Data.Models.NES
         /// </summary>
         public CPUPPUTiming CPUPPUTiming { get; set; }
 
+        #region Byte 13
+
+        #region Standard System and PlayChoice-10
+
         /// <summary>
-        /// Vs. System Type and Extended Console Type
+        /// Reserved byte, unused
         /// </summary>
         /// <remarks>
-        /// When Byte 7 AND 3 =1: Vs. System Type
-        /// When Byte 7 AND 3 =3: Extended Console Type
+        /// Valid when <see cref="Header.ConsoleType"/> == <see cref="ConsoleType.StandardSystem"/>.
+        /// Valid when <see cref="Header.ConsoleType"/> == <see cref="ConsoleType.PlayChoice10"/>.
         /// </remarks>
-        public byte ExtendedSystemType { get; set; }
+        public byte Reserved13 { get; set; }
+
+        #endregion
+
+        #region Vs. Unisystem
+
+        /// <summary>
+        /// Vs. System Type
+        /// </summary>
+        /// <remarks>
+        /// Byte 13, Bits 0-3
+        ///
+        /// Valid when <see cref="Header.ConsoleType"/> == <see cref="ConsoleType.VSUnisystem"/>
+        /// </remarks>
+        public VsSystemType VsSystemType { get; set; }
+
+        /// <summary>
+        /// Vs. Hardware Type
+        /// </summary>
+        /// <remarks>
+        /// Byte 13, Bits 4-7
+        ///
+        /// Valid when <see cref="Header.ConsoleType"/> == <see cref="ConsoleType.VSUnisystem"/>
+        /// </remarks>
+        public VsHardwareType VsHardwareType { get; set; }
+
+        #endregion
+
+        #region Extended Console Type
+
+        /// <summary>
+        /// Extended Console Type
+        /// </summary>
+        /// <remarks>
+        /// Byte 13, Bits 0-3
+        ///
+        /// Valid when <see cref="Header.ConsoleType"/> == <see cref="ConsoleType.ExtendedConsoleType"/>
+        /// </remarks>
+        public ExtendedConsoleType ExtendedConsoleType { get; set; }
+
+        /// <summary>
+        /// Unknown reserved bits
+        /// </summary>
+        /// <remarks>Byte 13, Bits 4-7</remarks>
+        public byte Byte13ReservedBits47 { get; set; }
+
+        #endregion
+
+        #endregion
 
         /// <summary>
         /// Number of miscellaneous ROMs present
diff --git a/SabreTools.Serialization/Readers/NESCart.cs b/SabreTools.Serialization/Readers/NESCart.cs
index c0a21b40..ab1b36da 100644
--- a/SabreTools.Serialization/Readers/NESCart.cs
+++ b/SabreTools.Serialization/Readers/NESCart.cs
@@ -147,7 +147,24 @@ namespace SabreTools.Serialization.Readers
                 obj.ChrNvramShiftCount = (byte)((byte11 >> 4) & 0x0F);
 
                 obj.CPUPPUTiming = (CPUPPUTiming)data.ReadByteValue();
-                obj.ExtendedSystemType = data.ReadByteValue();
+
+                // Byte 13
+                byte byte13 = data.ReadByteValue();
+                if (obj.ConsoleType == ConsoleType.VSUnisystem)
+                {
+                    obj.VsSystemType = (VsSystemType)(byte13 & 0x0F);
+                    obj.VsHardwareType = (VsHardwareType)((byte13 >> 4) & 0x0F);
+                }
+                else if (obj.ConsoleType == ConsoleType.ExtendedConsoleType)
+                {
+                    obj.ExtendedConsoleType = (ExtendedConsoleType)(byte13 & 0x0F);
+                    obj.Byte13ReservedBits47 = (byte)((byte13 >> 4) & 0x0F);
+                }
+                else
+                {
+                    obj.Reserved13 = byte13;
+                }
+
                 obj.MiscellaneousROMs = data.ReadByteValue();
                 obj.DefaultExpansionDevice = (DefaultExpansionDevice)data.ReadByteValue();
 
@@ -181,10 +198,10 @@ namespace SabreTools.Serialization.Readers
                 // Byte 10
                 byte byte10 = data.ReadByteValue();
                 obj.TVSystemExtended = (TVSystemExtended)(byte10 & 0x03);
-                obj.ReservedBits23 = (byte)((byte10 >> 2) & 0x03);
+                obj.Byte10ReservedBits23 = (byte)((byte10 >> 2) & 0x03);
                 obj.PrgRamPresent = ((byte10 >> 4) & 0x01) == 0x01;
                 obj.HasBusConflicts = ((byte10 >> 5) & 0x01) == 0x01;
-                obj.ReservedBits67 = (byte)((byte10 >> 6) & 0x03);
+                obj.Byte10ReservedBits67 = (byte)((byte10 >> 6) & 0x03);
 
                 obj.Padding = data.ReadBytes(5);
 
diff --git a/SabreTools.Serialization/Wrappers/NESCart.Printing.cs b/SabreTools.Serialization/Wrappers/NESCart.Printing.cs
index 3afd50e0..4a0889ee 100644
--- a/SabreTools.Serialization/Wrappers/NESCart.Printing.cs
+++ b/SabreTools.Serialization/Wrappers/NESCart.Printing.cs
@@ -104,7 +104,7 @@ namespace SabreTools.Serialization.Wrappers
                 builder.AppendLine(tvSystemExtended, "    TV System Extended");
 
                 // Bits 2-3
-                builder.AppendLine(header1.ReservedBits23, "    Reserved bits 1-2");
+                builder.AppendLine(header1.Byte10ReservedBits23, "    Reserved bits 1-2");
 
                 // Bit 4
                 string prgRamPresent = header1.PrgRamPresent ? "Present" : "Not present";
@@ -114,7 +114,7 @@ namespace SabreTools.Serialization.Wrappers
                 builder.AppendLine(header1.HasBusConflicts, "    Has Bus Conflicts");
 
                 // Bits 6-7
-                builder.AppendLine(header1.ReservedBits67, "    Reserved bits 6-7");
+                builder.AppendLine(header1.Byte10ReservedBits67, "    Reserved bits 6-7");
 
                 #endregion
 
@@ -166,20 +166,23 @@ namespace SabreTools.Serialization.Wrappers
                 // Byte 13
                 if (header.ConsoleType == ConsoleType.ExtendedConsoleType)
                 {
-                    ExtendedConsoleType extendedConsoleType = (ExtendedConsoleType)(header2.ExtendedSystemType & 0x0F);
-                    string extendedConsoleTypeString = extendedConsoleType.FromExtendedConsoleType();
+                    string extendedConsoleTypeString = header2.ExtendedConsoleType.FromExtendedConsoleType();
                     builder.AppendLine(extendedConsoleTypeString, "  Extended console type");
+
+                    builder.AppendLine(extendedConsoleTypeString, "  Reserved bits");
                 }
                 else if (header.ConsoleType == ConsoleType.VSUnisystem)
                 {
-                    VsSystemType vsSystemType = (VsSystemType)(header2.ExtendedSystemType & 0x0F);
-                    string vsSystemTypeString = vsSystemType.FromVsSystemType();
+                    string vsSystemTypeString = header2.VsSystemType.FromVsSystemType();
                     builder.AppendLine(vsSystemTypeString, "  Vs. system type");
 
-                    VsHardwareType vsHardwareType = (VsHardwareType)(header2.ExtendedSystemType >> 4);
-                    string vsHardwareTypeString = vsHardwareType.FromVsHardwareType();
+                    string vsHardwareTypeString = header2.VsHardwareType.FromVsHardwareType();
                     builder.AppendLine(vsHardwareTypeString, "  Vs. hardware type");
                 }
+                else
+                {
+                    builder.AppendLine(header2.Reserved13, "  Reserved");
+                }
 
                 // Byte 14
                 builder.AppendLine(header2.MiscellaneousROMs, "  Number of miscellaneous ROMs");
diff --git a/SabreTools.Serialization/Wrappers/NESCart.cs b/SabreTools.Serialization/Wrappers/NESCart.cs
index fb511ca1..1f8e674a 100644
--- a/SabreTools.Serialization/Wrappers/NESCart.cs
+++ b/SabreTools.Serialization/Wrappers/NESCart.cs
@@ -281,7 +281,7 @@ namespace SabreTools.Serialization.Wrappers
                 if (ConsoleType != ConsoleType.ExtendedConsoleType)
                     return ExtendedConsoleType.RegularSystem;
 
-                return (ExtendedConsoleType)(header2.ExtendedSystemType & 0x0F);
+                return header2.ExtendedConsoleType;
             }
         }
 
@@ -347,7 +347,7 @@ namespace SabreTools.Serialization.Wrappers
                 if (ConsoleType != ConsoleType.VSUnisystem)
                     return VsHardwareType.VsUnisystem;
 
-                return (VsHardwareType)(header2.ExtendedSystemType >> 4);
+                return header2.VsHardwareType;
             }
         }
 
@@ -367,7 +367,7 @@ namespace SabreTools.Serialization.Wrappers
                 if (ConsoleType != ConsoleType.VSUnisystem)
                     return VsSystemType.AnyRP2C03RC2C03Variant;
 
-                return (VsSystemType)(header2.ExtendedSystemType & 0x0F);
+                return header2.VsSystemType;
             }
         }