When: Ca. 1956, based on the slide mount and elements of the photo.
Where: Victoria, BC. There were other slides in the batch that hinted to this being Victoria, and a Bing search of the bird's eye imagery helped me to find the distant building prominent on the skyline. It then became an easy matter to find the specific location based upon the greenery in the foreground.
Who: Lots of folks, but all are anonymous.
How (much): Picked from a set of three filled Kodaslide boxes that I picked up from ebay for $12.99. While certainly not all of them were the gold that this one is, there are actually a number of gems in the mix as well, including Kodachrome Classic Monday #32.