First Commodore monitor, the Commodore 1701 video monitor is introduced on 1983 Winter Consumer Electronics Show, Las Vegas, January 6-9 source), so it is not period correct for early Commodore 64 computers (like C64 with silver label badge) and old Vic-20 computers (before rainbow lines badge).
That times most users use these computers on a TV, but I was curious what should be a period correct monitor for an early Commodore 64.
And I have looked Commodore 64 and Vic-20 boxes what things on it.
Vic-20 boxes uses TVs only (or nothing).
Early North-American C64 boxes are also uses TVs but a monitor too!
This picture from ebay.com
I have searched a lot and I have found it.
This monitor is AMDEK Color-I :
This picture from www.reddit.com
This picture from Recycledgoods.com
Early European C64 boxes are also uses TVs and a freaky monitor too!
This picture from Bo Zimmermann
This picture from nightfallcrew.com
It was harder but I have found it!
This is Blaupunkt CQM 67-120 C :
This picture from radiomuseum.org.jpg