A600 NTSC and PAL can't be identical:
- PAL and NTSC Amigas have different main crystal frequency.
- Different internal RF modulator.
- Internal PAL composite encoder needs extra components that are most likely not installed in NTSC version to reduce cost.
- 8375 Agnus used in A600 does not have external PAL/NTSC pin, default boot up display mode is internally hardwired. 8375 has PAL and NTSC variants. (Only 8372 has PAL/NTSC pin)
EDIT: - A600 schematics shows NTSC/PAL differences