Probably in the $350 - $400 range depending on condition, barrel length, etc.
If you had the box & papers it would be worth probably at least $100 more.
This one just sold for $361+, and that would be cheap in this part of the country.
Course, if you add in shipping a handgun & FFL fee's on this one, you are over 4 bills!
http://www.auctionarms.com/search/displayitem.cfm?itemnum=8475801
The Challenger was a slightly less expensive version of the 2nd. series Woodsman.
They were only made from May 1950 to Aug. 1955.
The 4 1/2" guns generally bring slightly more then the 6" ones.
Regardless, IMO, it is one of the finest sport .22 pistols ever made.
One of the true classics we will never see the likes of again!
PS: Here are take-down instructions & everything else you could want to know:
http://www.eskimo.com/~rayburn/woodsman/cwpg.html
rcmodel