I'm not aware of any cedar-topped D-25 either, especially from 1975ish which would be an arch-back. It would be an odd combination to have the usual D-25 arch-back with a cedar top, to me anyway. I don't think I've ever played a cedar topped arch-back. Cedar makes a wonderful soundboard wood, albeit usually not as durable as spruce or mahogany. I know there aren't many 12-strings with cedar tops because often they won't hold up to the string tension.
It is supposed to be a slightly softer wood, wouldn't surprise me if that's the primary reason it's not often seen on 12-ers. Or perhaps doesn't "chime" enough?
So, I'm assuming the DV-6 cedar version had a solid back, right?
A-yup, just had cedar tops. IIRC there were only 6 (the usual build increment) or a very small number like 12.
I read that the arch back started in 76, this guitar was not an arch back
No, the arched back actually started appearing in '73 while they still had 'hog tops. The most all-hog archback D25 sightings are from '73, then spruce tops became predominant, pretty much completely replacing 'hog tops by late '74 except for a few outliers.
I always remember member Spiderman had what he claimed was a '76 all-'hog archback, for one. I was skeptical and suspected it must have actually been a mahogany-stained spruce top version, but now I'll take his word for it, with all the oddities I've seen in the intervening years.
Since it was a flatback, I suspect you really did have a DV6 cedar.