I have a lot of Snap-on BSF tools...
Let's see yours too, Al!
I just gave these away on GG pay it forward:
Heyco whitworth wrenches:

From the responses I don't think that many understand whitworth sizes. My understanding is that the size refers to the bolt size. So, if you grab a 3/8W it would equal a 9/16 sae wrench. Is this correct Papaw?
Chilly
Edit: I measured the wrenches, here are the results:
1/8W = slightly under 3/8"
3/16W = slightly over 7/16"
1/4W = 17/32"
5/16W = slightly over 19/32"
3/8W = 11/16" (disproving my previous theory)
7/16W = slightly over 13/16"
1/2W = 15/16"
I have no idea what this means without further research....