Terence Wise, in his Osprey Flags of the Napoleonic Wars (2), states that Prussian Landwehr units did not have flags according to official regulations but nevertheless there is some evidence that many of these units did carry flags. He goes on to say that many of the Silesian Landwehr units are believed to have carried sky blue flags bearing the red and white checkered, gold crowned, heraldic eagle of Silesia.
I tried to find a website to see what this looked like and came up with the one below showing the shield of the Czech Republic which incorporates heraldic lions of Bohemia with the heraldic eagles of Silesia and Moravia.
The problem is that the description in Terence Wise's book does not fit the Silesian Eagle in the Czech Republic shield. It is the Moravian Eagle which is red and white checkered on a blue background, whilst the Silesian one is black, with a white sash across its wings and breast, on a yellow background. Prussian Silesian troops had yellow facings so it seems to me that this is more likely.
I suppose it is possible that Moravia was part of Silesia in the Napoleonic era and troops from that region did carry flags of the description given by Terence Wise. I just do not know the boundaries in this period well enough to speculate on this.
Can anyone throw some light on this?