Ben,
I think what you have there is Herters version of a Vickerman. Still a excellent seater!
Here is a picture of both. I lucked into the Herters in Nov at a local gun show. I didn't even know that Herters made this type, until I bought it. Mines in 303 British and I got the sizing die with it. I have a nice P14 but, had been loading it it with a 308 die set so, it was a wonderful find.
Frank