Screwback GAB's, IAB's and even PAB's and clasps to the EK are known or at least by consensus are considered to be of period manufacture.
Deumer and Juncker factory produced (special orders) Gab's.
Special orders also resulted in IAB examples.
Jewler transformations and in field conversions account for some IAB's, GAB's and PAB's in a screwback configuration.
I feel screwbacks are rare to find. Like many badges and awards fakes exist.
Kevin S., would you care to open a discussion on your example? I am not at all sure about it.
--dj--Joe
