Hey there, I believe it is likely to be an enhancement core. There were circumstances that could cause them to go the postmaster as engrams, they looked like Exotic Engrams but decrypted into cores. I remember that opening Dawning packages while your Engram inventory was full, could do it (cores needed an empty engram slot, for some reason). At some point they fixed this behaviour, but there was a short period of time where they'd still get awarded as an invisible engram, taking up space. Yes, just dismantle.