I understand they do have the full 1MB Chip so if you turn it on, you'll know for sure. A lot of them were fitted with KS1.3 ROMS though so you'll have to boot into Workbench to see, won't be obvious from the insert disk screen.
Or pop the trapdoor cover off and see if you can feel a battery? Can't remember if you can get a finger through there, but on a + board the clock battery sits right above the trapdoor so you might be able to feel/see it.