I've had this laying around for a number of years and have used it a few times when a tight situation made a normal Stilson style impractical.  I don't remember where I got it...most likely in an auction lot where I was really going after something else.  It appears to have only minimal use.  The number "350" in the bottom pic refers to the 350mm length.

Hello, John, from a fellow tool guy. I have a similar wrench, and it has in raised figures inside the recessed panel; LITTLE GIANT FEB  4 1913. You can look up the patent info on the DATAMP website. Regards, Lou

I have a Little Giant too. Made by Greenfield Tap & die Corp, Greenfield MA. Patented by Addison B. Carll. Also listed in Copes and Schulz #600. Mine is in my user pile when I need to do plumbing around the house.

Part of my inheritance from my uncle was one pipe wrench with the jaw set at 45 degrees, which has been similarly useful in tight spots.

With my son's help, we're slowly moving toward copper pipe, so the pipe wrenches are, increasingly, limited to the gas lines.

Garrington Is made in the UK if I am not mistaken.

"Garrington Is made in the UK if I am not mistaken."

Correct.  That is stated elsewhere on the handle, on a part that does not show in my pics.  In my searching about for info on the company I found this:
http://www.historywebsite.co.uk/articles/Darlaston/Garringtons.htm

...Which, sadly, means that they were made in England

For some period of time, Garrington wrench models were given "bird" names.  Hunt up a photo of the "THE GREBE" for a really distinctive form.

It looks like the moveable jaw is reversible on the tool body, with ridges on both sides. Is this for when it wears out you can flip it over and have a fresh set of teeth? Or is there more to it?

The Lapwing jaw can be used in 2 different positions. The Little Giant Jaw can be used in 4 different positions. Not sure of the reasoning behind it. I'm sure there must be times when you need the different arrangements to get into tight places plus like you said it will give you another set of jaws to use.