Why are the Convair 880's yokes shaped differently from each other? Looking at this picture of a Convair 880's flight deck...



(Image originally by the San Diego Air &amp; Space Museum at Flickr, via Wikimedia Commons)

...the captain's and first officer's control yokes have quite different shapes; the captain's yoke is round, like that of an automobile or a 1930s propliner, while the first officer's yoke has the familiar W-shaped yoke, complete with buttons on the yoke's horns.

Why the difference between the two yokes?  Is it to optimise the captain's yoke for the duties of a pilot flying, and the first officer's yoke for the duties of a pilot monitoring?  Or something else?
My guess is that this is a relatively odd situation, where one yoke had already been replaced by a newer one (on the right), whereas the other still is the original. 

If you look at the two images below (from Airliners.net), both yokes are the same.




It seems as if the right one has some more controls on the yoke (e.g. for radio settings, trim controls, or something else) and is simply an upgrade to the older model. If the old one still worked, I can imagine an airline waiting for a regular service inspection or overhaul before replacing it, rather than removing parts that are still fit to fly.