The rectangular mask really shrinks the face of the 19" tube. That, coupled with the fact that the cabinet is big as a combo, makes it look like a 15" set if you don't have a reference to scale.
Here's a pic of mine, which has a 21" tube...
...better illustrating just what a massive beast the 205 is.
I have seen half of the surviving sets; none of them have the earlier CBS-Columbia script logo as illustrated in the ad.