[B]Zenith Service Info.,or Sam's, for Zenith: T2851W2[/B]

[dieseljeep]

That's another of those odd-ball Zenith models, like the 20BC50. It didn't have 20 tubes, so it didn't follow the original Zenith chassis numbering system.
They must've made enough of them, for Sams to print a folder for them.