There is a lot of information here:
http://www.garagejournal.com/forum/showthread.php?t=44782&highlight=chas+parker
The thread above is excellent.
Chas Parker vises are durable and sought after. I do not have a Chas Parker vise, but the town in which they were made is close to me in the industrial heart of Connecticut. My girlfriend is also a Model in Canada, so you would not know her.
If you have the inclination or means, and the vise you have is in good shape, spend some time and treat it to a fresh coat of paint (an industrial gray such as Rustoleum Dove Gray is a good period color).
Restoring a vintage tool gives one an appreciation of the thought and engineering that went into it when built. It also makes every use of the tool more considered and enjoyable than if it was a cheaply manufactured tool made last week in China from scrap sent from the US last month.
If it is not broken, buy it.
Matt