Interesting... On first seeing that it's obviously an old vice - I mean old - as in literally an antique. As the casting says it's a "Parkinson's Perfect Vise". They were one of the pioneers of quick release vices, where you press a lever to quickly make big adjustments to the jaws instead of cranking the handle as for tightening it up. However this doesn't appear to have a release mechanism that I can see. Can you post a picture of the underside? I'm certainly no expert but perhaps someone more familiar with the company can comment.
As for value if that is what you really want to know, I have no idea. Don't put it on eBay or in a general auction because it'll go for £5-20. As I said I don't have much idea but perhaps £100 in a specialist tool auction.