That does look like a standard, non QR vice at first glance. That nut assembly does appear somewhat unusual though. I'd be intrigued to see some photo's of that unit completely disassembled, as it does seem that the nut may be, (bearing in mind it's hard to make out from that photo), split along its length vertically and hinged at the bottom. You have me intrigued now, for definite. The leadscrew also seems to be a much finer pitch than I'd expect to see. and in case anyone is wondering how to generally tell an English, (not sure what, if any, method you tend to use on the vices over there?), QR vice from a standard one, it's this lever, (the styling of the leadscrew collar and lever may vary slightly, but they're usually very similar no matter the brand or model), which is the giveaway.
Saying that though, I've never paid any of the latter day or Irwin Record's the slightest attention upto just, hence why I've never seen that setup before. You've piqued my curiosity no end with that setup now. 
