How To Tell Germany Scott 411 Or 428?

One more, here we have a picture of 2 German stamps that look alike.

Stamp on the right paper looks yellower than on the left. How can I tell whether these are German Scott 411 or 428?

Thanks.

The difference is in the watermark. Watermarks are applied to stamp paper before printing to discourage counterfeiting. You can see the watermark by placing the stamp in a dark tray and immersing it in commercially available watermark detection fluid.

Both are 50 pfennig stamps showing German President von Hindenburg.
Scott 411 was issued in 1933 on paper with watermark type 126, which has a fishnet pattern:



Scott 428 was issued in 1934 on paper with watermark type 237, which has a pattern of Nazi swastikas:



So the political changes in Germany in the early 1930s are evident in the changes in the watermarks.

Watermark detection fluid can be purchased from any dealer in stamp supplies, for example Amos Advantage.

Thanks, I assume that is the only way to safely tell?

A specialist in German stamps may be able to classify them based on his experience, from the difference in the darkness of the central part of the design or slight differences in paper. Still he would check the watermark to confirm. You might be able to see the watermark without using fluid if you hold the stamps up to an intensity lamp. In the old days we used benzene and a black ashtray. However since benzene is a carcinogen it is no longer used.