So in short there were 2 different D 25s (arched back and flatback), a D 15, and now there is a D 20 too. D 15s, D 25s archback, and D 20s are all hog guitars (?), when flatback D 25s may have other woods for back & sides, is that right ? (maybe not that bad to make it more simple
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The D 15 Adorski posted last page looks exactly like the guitar the guy I knew have...So if his is a D 25, he possibly called it D 20 after becoming aware of the new guild nomenklatura (he's been working in a music shop for a while some years ago). His guitar has a flat back though...I'll have to ask him. Thanks Ralf for your post : it is very instructive.