Birdcage stuff. Mike, (yes I am old enough to know...) Many old German uprights of that vintage have an "attached" action. To get the thing out you slide the key frame (with the keys of course) out and the action comes out with it. Behind it you will find an (up and down) adjustable rail which stops the keys from bottoming. That rail acts as a "dip adjustment". All the above is of course is only true if you and I are talking about the same kind of piano... Hope it helps.
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