These are not stop names, but modifiers which indicate a doubled stop; that is, having two pipes per note. They are mentioned only by Adlung, who writes: Doppelt is a word that does not denote any particular stop, but rather is used if a stop is doubled. For example at Jena there is a �Contrabass 32' doppelt�; since an open 16' is also present. At Gera there is a �Vox humana doppelt�, as well as a Flötedouce 8'; see �.301. ... This much may be said about the Doppelflöte: it is not unheard of for two pipes to be placed on each key, and consequently this interpretation is indeed possible. In this case it would be the same as the Duiflöt if the latter is sometimes conceived in the same way; see �.137. �Duplicat� likewise means the same thing as these words; for [Praetorius] continues: �Offen Chormass of a special type, Oktave, duplicat this.� Once again, this means either that the previous 2 stops, Offen Chormass and Oktave, are upon the same hole, or that they are both controlled one stop mechanism. And thus proceeds the rest. One ought to consult Praetorius, loc. cit., for oneself.
No examples are known except for those cited above. Contributions welcome.