Please explain this tool:

[Peter C]

It actually has "6 - 8 in" marked on the handle - how that works with an adjustable wrench I can't figure, unless one head is bigger that the other, maybe disguised by the perspective of the photo.
The longer I look at it the more confused I get - is one thumbwheel the opposite to the other, ie, LH/RH?
I can't stand the old Bahco I used to have, with it's thumbwheel opening the jaws when most adjustables would be closing them!

Yeh, I reckon one head is bigger than the other to cater for smaller or larger range screws.

 

[Greenpeace]

Yeh, I reckon one head is bigger than the other to cater for smaller or larger range screws.

That is correct, they used to do 4/6", 6/8", 8/10" and 10/12" in Diamond Calk brand, not sure about Crescent's range though, I've seen both 6/8" and 8/10", but there could be more. The sizing refers to their standard corresponding size shifter's jaws.

 

[Kim Luck]

Some of youse may not be old enough to remember that in 1964 the RAAF introduced the French Mirage 111O to replace the US designed and Australian built CAC-27 Sabre. The only Metric tools we had at the time were various sized shifters and Phillips screwdrivers with the tips ground off to fit the Dassault screws. One size shifter fitted virtually everything the Frogs could throw at us, it was our first metric tool.