Looks like a disk sector to me too. However the partition table
is further on. See:

https://en.wikipedia.org/wiki/Master_boot_record#Sector_layout

So that reference says the "classical generic MBR" partition entry # 1 is offset 0x1BE.

Which in this image is right in the error strings (?) section.

00000170 13 59 5A 58 72 09 40 75 01 42 03 5E 0B E2 CC C3 .YZXr.@u.B.^.âÌÃ

00000180 03 18 01 27 0D 0A 49 6E 76 61 6C 69 64 20 73 79 ...'..Invalid sy

00000190 73 74 65 6D 20 64 69 73 6B FF 0D 0A 44 69 73 6B stem diskÿ..Disk

000001A0 20 49 2F 4F 20 65 72 72 6F 72 FF 0D 0A 52 65 70 I/O errorÿ..Rep

000001B0 6C 61 63 65 20 74 68 65 20 64 69 73 6B 2C 20 61 lace the disk, a

000001C0 6E 64 20 74 68 65 6E 20 70 72 65 73 73 20 61 6E nd then press an

000001D0 79 20 6B 65 79 0D 0A 00 49 4F 20 20 20 20 20 20 y key...IO

000001E0 53 59 53 4D 53 44 4F 53 20 20 20 53 59 53 80 01 SYSMSDOS SYS€.

000001F0 00 57 49 4E 42 4F 4F 54 20 53 59 53 00 00 55 AA .WINBOOT SYS..Uª

00000200 F8 FF FF FF FF FF 04 00 FF FF 06 00 FF FF 08 00 øÿÿÿÿÿ..ÿÿ..ÿÿ..

So if that is where guestfish is looking for the partition table...

I searched for other references. Found this one and it agreed with this 0x1BE value.

Any other locations that you know of?