Fine to find you here !
Indeed, the Wagner organs allow the player to have or not tierces in the chorus; there is no tierce
in the Mixture, but well in the "Scharff" (4/5'- 1 3/5'). It is so in all his organs.
You can hear the complete chorus here:http://www.youtube.com/watch?v=m8A07eFGB-c&feature=related
(The Angermünde organ was one of my pilgrinage places, one of my preffered organs...)
J. Wagner worked during a time with Silbermann (two years ? This is not precisely known), but his master,
unknown, belonged to the northern school, so that his own style is an incredibly successful synthesis
of central-german, northern, and french ones.
The reed stops may lend towards Silbermann, but on the video I linked to you can hear a rather Schnitger-like
Trompete, while the Vox humana he built after french measures (but with trompete's shallots !)