Wayne,
I think this is the best address to try in the first instance:
Superintendentur Gera
Talstrasse 30
D-07545 Gera
Germany
You need to enquire about the Kirchenbuecher (parish registers).
The Lummer family were well-known in Gera as industrialists and bakers; their origins being in the small village of Untermhaus, just outside Gera.
Justin