Thank you Anne, you are really a star!
I had also asked Glen directly before the photos appeared here and she was so kind to answer (thanks also to you, Glen!) Debra that she does not believe it is Carnival which Debra meanwhile confirmed, the plate is simply a golden yellow. (Must have been my screen that made it look iridized

)
Pattern and shape: Glen also confirms my opinion that Brockwitz made this Greek Key and Flower pattern, it appeared in the 1915 catalogue, however not in this
square shape.
Marcus, the Streit bowls and plates are
octagonal, round or oval - I am unable to find a square one. You get an idea of the size of Debra's plate from the photo in which she is holding it in hand.
Regarding the base: Debra's plate shows four straight rows of four flowers each, no mark (otherwise it wouldn't be here

)
Streit's base bears rows of 3/5/5/5/3 flowers, some of them cut off at the outer rim, and mostly is marked in the centre (instead of flower):
http://www.pressglas-pavillon.de/schalen/03598.html round plate
http://www.pressglas-pavillon.de/schalen/05256.html octagonal dish
http://www.pressglas-pavillon.de/schalen/04775.html large bread dish with additional design on the rim
Finally I like you to compare the rim: Debra's is a band of flowers, Streit's is smooth and curved
I have of course invited Debra to join us here

She thanks you all very much for your interest!