.... I always referred to them as mini capsan winches.......
All the early boxes had them...... and if you search the archive pictures from CLive you will see that the early box canvas had some kind of leather strap with keyholes in them.... they fitted over them funny little "whatever"..... all early boxes also had the curves hooks welded to the box and they seemed to be used to secure a short tarp over the box when the "bows" were not used.... again this is based on factory pictures from Clive.....
It would make sense that with field experience the typical metal spring hood type clasps where used on the tarps to secure the tarp under some tension yet could be very quickly released for battle situations.
Grant has reproduced some very accurate copies of the spring devices.... even importing the suitable springs from the USA in yard long strips from an outfit that would not ship to Canadians even when using a UPS box in Ogdensburg...... he used the good services and good will of Phil in NH to remail to the barn...... the Caldwells are also reproducing them as well.
Boob
PS the link from Rob worked for me......