Came across a mystery case, figured out it was a 20mm Solothurn 'long'.

 

 

Cleaned up well after a bath of white vinegar. 

 

 

'P490' headstamp turned out to be Hugo Schneider AG (HASAG) made in 1938, Paunsdorf, near Leipzig. This was one of Germany's largest Arms factories, established in 1863. During the outbreak of the war, HASAG expanded and created 8 more factories, including 3 in Poland.  

 

 

Per the Spanish collector site Municion.org, this particular headstamp indicated a wooden projectile blank load.

 http://old.municion.org/20mm/20x135.htm

Interesting.  Do you think the wooden blank was a training or practice round?  

I get the sense it was a training round, as there were solid 'training' rounds.

 

Another tidbit - that knurling 1/3rd of the way up the case indicates that it was reloaded.

With a dummy HE-T stand-in projectile. Interesting that these rounds were not only used in Solothurn and Lahti AT rifles, but Breda AA and several German Flak guns.