告白教会
However, other events, such as collections of money for purposes of the Confessing Church, meetings of its adherents or elections of their "brethren council", paralleling the "German Christian"-dominated presbytery, were forbidden to take place as events open for the public, but only card-carrying members of the opposing Confessing Church were allowed. Grüber carried the – due to their colour so-called – "Red Card" No. 4, issued on 22 December 1934 by the Kaulsdorf Confessing congregation.