I know for a fact that it is a Columbia and it seems to be a 1961, 1962 or 1963 model, in a new post below are several pics I have dug up, all but one of these bikes are 1961 bikes and the one that is 1962 looks like the ladies version of what I have accept the chain guard is different, these are the only three years I can find that use that chain guard design, years before or after are different.
Go to this link and take a look at the pics when you get a chance and you'll see what I mean.
Originally Posted by 2door
Shan, whatever it is it used to have fenders. Too bad those are missing. If they had the same look as the chain guard they were probably cool too. Let us know what you find out. If all else fails I know a guy here in Denver who could probably identify it but he's an idiot and I don't like talking to him.