Hoooo boy, the HB torps. The hook nose is just embarrassing. :/
And would have no purpose on a warhead. Exersizeheads would have a hook though, but with a very different shape, and of course the head would have numerous features missing in this model (ref the photos of the black Molch displayed in Johannesburg, presented in the link with the review).
Note that the box-art for the model displays something that resembles the early (faulty) pistols G7A-MZ / G7A-AZ. These were not in use after late 1941, and would of course never have been used on a torpedo for a midget submarine...
a) Confirm the number of blade on each prop. (We know there were 2 props.)
As a general rule, all torpedoes have a pair of contra-rotating propellers to neutralize the torque-effect of the engine. The exeption is of course torpedoes with rocket or waterjet-propulsion, and the most early torpedodesigns, were they solved the problem initially by "twisting" the vertical fins to counteract the torque of the engine.
* All G7e variants have 2-blade propellers.
* The G7a-variants had initially 4 (later 6) blades.
b) G7e *does* or *does not* have fins behind the props?
There are two basic designs of the torpedo tail-piece:
"Whitehead" and "Woolwich" (presumabley named after the initial designer/manufacturer).
* The Whithead-tail has the propellers placed in front of the rudders (for example: G7a(TI))
* The Woolwich-tail has the propellers placed aft of the rudders (for example the G7e torpedoes).
No general rule, but the first variant were more common in the early days, and Woolwich is the most common tailpiece in modern torpedoes. It's a simpler design in most ways, but the Whitehead-tail is more robust (it was the main reason for the G7e-torpedo only being suitable for underwater launch, ie all german surface-vessels* used the G7a(TI) for the whole duration of WWII).
*One exepction: The G7es(TVa) "Zaunkönig", specially adaptet version for the S-Boote.
