KSEC1 element	Contents	GRIB octet	Recommended GRIB_API key	Coded GRIB_API keys	Comments
37	ECMWF local GRIB use definition identifier. 191 = Free format data descriptor	41	localDefinitionNumber	localDefinitionNumber
38	Class: 121 = general member state data	42	class	marsClass
39	Type	43	type	marsType
40	Stream	44-45	stream	marsStream
41	Version number or experiment identifier. (4 ASCII characters, right justified)	46-49	expver	experimentVersionNumber
42	Zero, for compatibility with Mars labelling	50
43	Zero, for compatibility with Mars labelling	51
44	Format version major number	52	formatVersionMajorNumber	formatVersionMajorNumber
45	Format version minor number	53	formatVersionMinorNumber	formatVersionMinorNumber
46	Original sub-centre identifier	54	originalSubCentreIdentifier	originalSubCentreIdentifier
47-50	Set to zero	55-58
51	Number of bytes of free format data descriptor (N, say)	59-60	numberOfBytesOfFreeFormatData	numberOfBytesOfFreeFormatData
52-(51+N/J)	Data descriptor bytes packed in integer array elements (J= the number of bytes in an integer = 4 or 8)	61-(60+N)	freeFormData	freeFormData	numberOfBytesOfFreeFormatData values.
-	The section is padded with zeroes to make the overall length of the section = 60 + 80*M for some M > 0	(61+N)-(60+80*M)