Isn’t the aperture change the reason you use the single element behind the aperture.
OP, B&L licensed the Protar from Zeiss so for the Protar V and Vii, the lenses are the same. For the most part Series IV lenses were very different. I believe yours is a Series VII.
You can find lots of old manuals at
https://www.cameraeccentric.com/
He has some problems that might cause your browser to show a warning, but just ignore the warning.
BTW, all of the Protar I’ve received have had the lower focal length on the front and the longer on the back. All of the Zeiss and B&L manuals above have the longer listed as the front lens. In use, I haven’t seen any difference.
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