According to Sinar Code catalogs, there were only two variants for P2: 4x5 standard (front 431.51 / rear 433.51) and special (front 431.52 comes with a frame, rear 433.52 is just the bearer).
EDIT: I think I figured out the mystery, the bearers in the middle are Sinar E (that have larger base...
I hope somebody of Sinar historians can shine some light as I couldn't find any information in catalogs, forums, or even from Sinar themselves.
I have Sinar P2 4x5 camera and I've recently got 8x10 conversion kit with special front and rear bearers (or at least that's what I thought).
Later...
That is great news! Thank you for doing that! I hope it'll get archived and preserved as there are a lot of valuable information that would be such a shame for it to disappear.
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