IIRC Zenith 27" started with Y line. ( 9-181 sets) The Sony 26 was the
first over 25" that I remember.
when I was a kid my father bought a BIG maggy B&W.
It was no UHF so '64 or before. It was biggest anyone made
then I think 27" ( advertized). It had that strange toned picture
I remember on old Maggies even noticable to me. It was a
toilet, junked in '67 for a Zenith color.
73 Zeno