Hochstetter's Uniform

I read somewhere that SS men like Hochstetter usually wore plain clothes, the fancy unifors were for parades and such.

Actually, Hochstetter shouldn't have worn a uniform at all, unless he was also in the Allgemeine-SS, as well as the Geheime Staatspolizei.

The black uniform was dropped by the Allgemeine-SS in 1942, and a gray uniform, similar in color to that of the Waffen-SS, but cut like the black uniform was adopted. The Gestapo was part of the RSHA, Reichssicherheits Hauptamt, and was under under the overall charge of Reichsfuehrer-SS Heinrich Himmler, and direct charge of SS-Gruppenfuehrer Heinrich Mueller. Not all Gestapo personnel were members of the Allgemeine-SS (the "general" SS), but most were, yet were plainclothes personnel due to the nature of their jobs.

Hochstetter's Gestapo rank wouldn't have been "Major," but Kriminalrat, which was the equivalent of Sturmbannfuehrer in the Waffen-SS. The equivalent US police rank would have been along the lines of a senior detective, or detective supervisor. His assignment seems to indicate that he was Department E1, Counterintelligence within the Reich. That indicates he might well have also had as assignment within the Gestapo's sister organization, Heydrich's Sicherheits Dienst, the notorious SD. If so, Hochstetter would have held both the Gestapo rank of Kriminalrat and the Allgemeine-SS rank of Sturmbannfuehrer. Because of the dual nature of his duty, Hochstetter would have worn the Mausgrau uniform on SD business, and plainclothes when on Gestapo business. Any armed enlisted men would have been Orpo (Ordnungspolizei--standard uniformed German police, possibly in shakos, more likely in Stahlhelm) or Waffen-SS enlisted personnel (Feldgrau uniforms).

If Hogan's Heroes were to be made more visually accurate, Hochstetter's uniform would have been Mausgrau, had the Totenkopf on the cap, the art deco Nazi eagle on his left sleeve rather than the Party armband, and since he said he'd joined the Party in 1931, he would have also had the Alte Kaempfer ("Old Fighter") chevron on his right sleeve. His shirt would have been tan (the Braunhemd or Brown Shirt of Nazi notoriety), tie black, and his Party badge and WWI and WWII military and SS decorations on his left pocket.

HH usually did pretty well with uniform accuracy...not too many blunders there, just issues raised due to budgetary constraints and the nature of Hollywood.

"It's a hard country, kid."

Short answer: Hochstetter was supposed to be Gestapo who wore no military uniform. The Gestapo were the Nazi's secret police who had power of both civilian and military alike.
Early on the Gestapo were under the umbrella of Herman Goering's authority, but were moved to Himmler's power along side the S.S., hence in the writer's mind could where S.S. uniforms too, I suppose. I don't think they actually did unless maybe in undercover investigations.
They usually wore clandestine raincoats and hats (which was really very UN-clandestine, LOL.)

was it Hochstetter? or simply Howard Caine... IIRC he appeared twice before they settled on Hochstetter

-- and there was a Non-Gestapo General Hochstetter who appeared in one season 1 episode as well