What are crank pliers?

[Chippychap]

Hi guys, I recently inherited my father-in-law's belongings and am assimilating his tools with mine.

One hand tool has me absolutely baffled.

My F-I-L had no link with aviation but, like me, was interested in interesting bits and bobs.





This bod-

http://www.militaryantiques.co.uk/sh...cat=397&jump=6

-has one similar but his and mine have no crowsfoot mark.

Any ideas guys?