Any idea of a possibly German made 20mm projectile?

[Tmine35]

This inert 20 mm HE-shell is in an experimental Finnish 20x98B L-37 aiplane gun round. However it is totally untypical to any other Finnish shells of the era. Fuze thread is M17x1mm ( normally they are M15x1mm ). Driving band is very special narrow. It is assumed that these shells were purchased from Germany or Switzerland in mid 1930's. In any other Finnish experimental 20mm rounds I have seen only AP-shells so far.

No markings on shell, only dark field grey paint. I can't pull the projectile but there might be space for a tracer cavity at aft end.
Shell is 48,5mm long from below fuze to below driving band.

Does anyone have any detail information about such earlier ( German? ) shells?

Another question is what is this fuze screwed on it? It obviously is not original but a post war replacement. However it clearly is for a 20mm round with M17x1mm thread.

 

[pzgr40/42]

The drivingband does look like something Swiss (oerlikon) or early German (Becker / Erhardt) in it's narrowness, but varieties of these kinds (Becker /Erhardt more or less exempt) of rounds have been produced in the millions worldwide, so without any markings it will be hard to find a definitive answer.

greetz,

Menno.

 

[Tmine35]

Thanks Menno,
Your thoughts are quite the same as mine. Finland used both mentioned guns in early 1930's as well - that was start of my thinking. Anyway projectiles shown for oerlikon and becker in Finnish manuals are different than this. Perhaps some confirmation could be found thru the large M17x1mm thread? Any drawings of mentioned projectiles available?