[HO455]

That would follow with the way the radios were marked. The cars got the brand on the dial or buttons and the the trucks said GM. At least until 69 or 70 I believe.
The same basic unit was offered for Pontiac's without any branding. 68-72 Grand Prixs were mounted on the drive line hump behind the front seats inside a vinyl box that matched the upholstery. Not very convenient. I had one I pulled out of a firebird in a wrecking yard for at least 15 years. I couldn't give it away. No one believed it was a factory unit or even wanted one. Finally traded it off with a bunch of other stuff as I was tired of storing it and packing it to and from swap meets. And now days they go for $1000 plus.
The brackets with the one in the thread are also different than the bracket that was on mine. Not that they look particularly special. Not meaning to dis them if they are factory correct.