'68 radio button question

[Guest dcdpgh]

Silly question - the radio buttons in my '68 do not have B-U-I-C-K on them like I see on most every other late sixties Riviera (and other Buicks for that matter). I suppose a previous owner could have swapped out the original radio at some point. So the question is, what year(s) did these radios not say B-U-I-C-K on the buttons? My car's interior is rather unmolested, and it's an early build '68 (September '67) if it matters. I know, not the most pressing question of the day, but I'm still curious.

[68RIVGS]

. . . a silly response Dan -

My '68 LeSabre had a plain jane 'Sonomatic' radio with no letters too, and it is now residing somewhere in Finland.

I've never seen another (. . . AM, FM, or FM Stereo) version without the letters, but my guess would be the 'letterless' versions might also have been installed in other GM vehicles ??

I'm quite sure one of the more knowledgeable Buick persons here will have the correct answer for us !!