Useful bits for /etc/magic:

#------------------------------------------------------------------------------
# Linux 8086 executable
0	lelong&0xFF0000FF 0xC30000E9	Linux-8086 executable, headerless
>5	string		.		
>>4	string		>\0		\b, libc version %s

0	lelong&0xFF00FFFF 0x04000301	Linux-8086 executable
>2	byte&0x01	!0		\b, unmapped zero page
>2	byte&0x20	0		\b, impure
>2	byte&0x20	!0
>>2	byte&0x10	!0		\b, A_EXEC
>2	byte&0x02	!0		\b, A_PAL
>2	byte&0x04	!0		\b, A_NSYM
>2	byte&0x08	!0		\b, A_STAND
>2	byte&0x40	!0		\b, A_PURE
>2	byte&0x80	!0		\b, A_TOVLY
>28     long            !0              \b, not stripped
>37	string		.		
>>36	string		>\0		\b, libc version %s

# Other ld86 executable formats ...
0	lelong 		0x10200301	Minix-386 executable
>28	long		!0		not stripped

0	lelong 		0x10100301	Minix-386 impure executable
>28	long		!0		not stripped

0	lelong&0xFF00FFFF 0x10000301	ld86 I80386 executable
>28	long		!0		not stripped

# Never seen formats.
# 0	belong&0xFFFF00FF 0x0103000B	ld86 M68K executable
# 0	belong&0xFFFF00FF 0x0103000C	ld86 NS16K executable
# 0	belong&0xFFFF00FF 0x01030017	ld86 SPARC executable

# AS86/LD86 object files.
# There is _no_ difference between 16 and 32 bit .o files that file can see.
0	string		\243\206\001\0	Linux-8086 object file