Wood C clamps

I have never seen clamps built in this fashion and I was eager to get my hands on this lost treasure.

Another garage sale item from the same gentleman who had the saw vise. Two assembly clamps made from beech wood. I believe the clamps are from Germany because of the stamped numbers on the handle end near the tenon corner. 18 and 21 are stamped respectively identifying the capacity of the jaw opening in centimeters. Actually the opening is more like 18.5 and 21.5 cm.

You may have noticed that the pads are missing from the wood screw. If the pads are roughly .5 cm then that would make the capacity exactly 18cm and 21 cm. This of course begs the question how were the pads attached and what shape did they take ?

Thread pitch of the screws are about 6 tpi.

Making reproductions of this clamp would be very fun and fairly straightforward.