There are a lot of potential red herrings on the ships design which throw off or suggest different eras.
Ball turrets really imply TOS/TMP
Blue impulse engines are evocative of Enterprise
The saucer rim is very TMP
The back neck line is very close to Voyager's
The warp engines have bits that evoke TOS, TMP, and TNG.
The deflector could easily be TMP or from the Enterprise-C era.
The indent ring on the saucer feels like it could be a nod to the Franklin, but it's also similar to an indent on the Excelsior.
The general coloring feels like it could be close to the same time as the Kelvin. Though, that is lighting and really doesn't say anything. That's just the feeling it evokes, to me.
Registry, in a broad sense, implies it would fall between Enterprise and TOS.
The font used is closer to something out of TMP, sans the bold/outline.
So honestly, it could be anything. There's just no way to know. It could very easily turn out to be a ship pulled through time and retrofitted with tech to keep it going. It could be an old ship pulled out of moth balls. It could be an experimental ship for deep space exploration... Who knows!