Dave,
Actually, the Teno was considered to be a voluntary police auxiliary and fell under the control of the Ministry of the Interior. They have their pre-NS origins in 1919 as you mentioned and some wore uniforms and some simply wore armbands and civilian clothing. Over the years the Teno became more important to the police and the NS Party and uniforms and insignia became more formal. Finally, they were uniformed like policemen with black insignia and piping. TN Polizei items are very scarce and sought after by police collectors.
Here is an example of the black piped TN Pol side cap. The cloth is police green and the eagle is standard but the black piping denotes this is a Teno Polizeimann.
George
