Bx that's not grounding?

[hurk27]

For safety I would treat anything that didn't meet the requirements of being an EGC as a ungrounded circuit, most of these old installs had 2 prong receptacles and the metal sheath of the old BX was not used as an EGC except when people installed 2 prong to 3 prong cheaters that had the small green wire to attach to the center screw of the cover, installing a GFCI just like you would for ungrounded circuits is a good idea as it would limit the fault current on it.