I have a number of British wrenches in the collection.  I also have those wrenches I suspect are British. This "Lion Brand" is one.  It has the following markings stamped at the ends on one side: "3/8 W" and "5/16 W". Turning the wrench over the corresponding markings are stamped "7/16 BSF" and "3/8 BSF".  In other words, "BSF" sizes are expressed  as being 1/16" larger than equivalent "W" sizes.

Are you able to identify this wrench as being British?

lion brand spanners were made by -armstrong stevens &co ltd of willenhall [staffs]founded 1835.
drop forgers.1920 taken over by ssp,sheffield steel products.which you may also find on spanners,ie jaguar kit spanners.
brian

Thanks, I knew you'd know!

1940:

Not just British, but sized for the (in)famous English standards, including "Whitworth" (or "Worthwhit" by those of a sarcastic mood; the "W" on one side of the wrench) and "British Standard Fine" (the "BSF" on the other side of the wrench).  These referred, I believe, to the diameter of the bolt, not to the measurements across the head; and the heads were standardized at the same size for different bolt diameters, depending on the thread pitch.

In spite of which, the British won the Battle of Britain and fielded a good many automobiles and motorcycles that dominated racing for years.  The mechanics must have been particularly nimble of mind to accommodate all those details in their brains.

Was once told BSF stood for Bloddy Sorta Fits....

Just remember it was Joseph Whitworth who first came up with the idea of standardisation of screw threads in 1841, at a time when every engineer and manufacturer in Europe and the USA were making their own taps and dies as well as the bolts they were using. BSW was the first national screw thread standard see: http://en.wikipedia.org/wiki/British_Standard_Whitworth, and one of the reasons the BSI (British Standards Institute) was founded in 1901. The SAE in the USA was not founded until 1905.

William Sellers did not produce the US standard thread until some years later in 1864, and followed much of Whitworths ideas except for using a different thread angle (60^o not 55^o) and flat topped thread rather than a rounded one. It was not adopted by SAE until 1906 see: http://en.wikipedia.org/wiki/United_States_Standard_thread

Can any one tell me if its worth anything ? , smith&sons of rodley , leeds built steam cranes back in the 1900 s