My D-18 is from 1969; I believe the serial number starts with 248...

The D-18 body is not rosewood like the other dreads, but mahogany. But from what you're telling us, my bridge plate would be rosewood. (I have no reason to doubt ~ I just never thought about that particular angle.)

I realize, of course, that the pre-war instruments are terrifically valuable ~ $8,000 is, of course, much higher than the $2500-3000 value generally assigned to 1969 models like mine.

But I feel pretty confident that my guitar is superior not only to any Chinese-made new guitar, it's probably better than most if not all current-day Martins.