BSA stands for Birmingham Small Arms and from what you describe is a BSA North American Model CF2 which was imported and distributed by Precision Sports Inc., Ithaca New York after 1968. This is BSA's updated version of the CF2 which is basically an upgraded version of the Monarch action. As unfired near perfect condition as you describe in my opinion be in the range of 700-900 US dollars. This is just a rough guesstimate as it's condition would have to be verified to establish a real value.
As this model BSA being a shooter I'm very satisfied by the one I have shot and it was not fussy about the diet it was fed. All bullets from 110 Gr trough 220 Gr were well within the half inch standard @ 100 yards.