Second hand nexus 5 Q?

I bought this nexus 5 from a previous user, noticed bootloader unlocked, diferente kernel(althought i flashed another already), but something caught my eye, im not sure if i have the stock rom, as i get an update of 16mb and fails.

"devcheck app"
Under system = Codename: Hammerhead
5.1.1
Build: LMY48I

Is this stock?