Going thru my tools I came on this die stock made by Pratt & Whitney prior to 1960 and three dies, 5/8-11 Whitworth, 5/8-11 BSW and 5/16 - 18 Whitworth.
I have quite a bit of P & W stuff. Size blocks, micrometers, drills, taps, dies and end mills. My father worked for P & W and I worked for another division of the company in the same building.
I have a lot of P&W machinist tools, they are basically the same as Lufkin as P&W bought Lufkin's machinist tool division. I have a NOS 0-1" mic in the original box. Can't say I've ever seen Whitworth dies, kinda cool.
I have english motorcycles from the 70's. While the frame and ancillaries were mostly changed to SAE by that era the engines, transmissions and primary drives are mostly still whitworth threads. A lot of us still use whitworth threading tools.