dump: Unknown

[777gamer]

i was using nestopia emulator and when i click in image info
some rom information pops up the real question is why it says dump: unknown? it could be a bad dump? here is after burner for example
File: After Burner (Japan).zip <After Burner (Japan).nes>
Directory: C:\Documents and Settings\Admin\Mis documentos\NES_COMPLETE\NES_COMPLETE\
Soft-patched: No
CRC: F2CE3641
SHA-1: BCD6794579A743211CF96A306EB97E74A0C33EF6
System: Famicom
Board: SUNSOFT 4, Mapper 68
PRG-ROM: 128k
CHR-ROM: 256k
Battery: No
Dump: Unknown

[Hiccup]

Sometimes it calls it a "good" or "bad" dump, I think. But AFAIK it is not reliable.