Is this a mistake?

[AlanClarke]

I was watching the first episode of the otherwise excellent British TV series "Secret Army" when I noticed that SS-Sturmbannführer Ludwig Kessler of the Gestapo has no SS insignia on his right collar. In fact, he never starts wearing one throughout the entire series. Is this a mistake or is there some historical precedent I'm not aware of.

[John G.]

Not a mistake.... while I haven't seen the series, he's probably portraying an SD officer, who worn a blank collar tab as shown.
John G.

[Mark in Cleveland, Tn.]

Good catch JohnG

[AlanClarke]

You are absolutely right. Later on in the show, I caught an SD badge on his sleeve.

[OakLeaves]

SD is correct , if you watch the new Norwegian film “ The 12th man “ you’ll see the same thing on the uniform of Kurt Stage . That and a triangular badge with the capital letters S and D on the left sleeve of the leather jacket he was wearing .