The second example card has a "squiggle" as a logo on the address side. An article on this company has appeared in The Postcard Annual no 34, which reveals that Gerhard Stummp, in his book "Halt gegen Licht" (ISBN 978-3-938543-3), shows that this is a specific shorthand version of Siberstein's name and that the publisher of these cards was Jacob Silberstein, München. Other logos used by Silverstein are shown in a seperate article here.
The figure you see when holding the example card to the light (you need a strong light) is also shown below. It is often rather spoiled by a stamp or writing, this is common for these cards - see the second example.
Another producer of this type of hold-to-light card was Kunstanstalt "Kosmos". The actual manufacturer of these cards may be another company of course. Maybe the book explains it.
TPA has an earlier article on hold-to-light which gives other examples.
