It looks to me like the plant that is sold, where I live, as Aloe "black gem." It is probably one of the Walmsley types, but I see almost no variegation. Many people also label Aloe black gem as an Alworthia -- cross of an Aloe with a Haworthia.

Variegation can dissapear in low light - at least that's my experience... I have it & it has been all green and variegated...Same plant, abt. 15mo apart

But if way too much sun, it could be very dark: