Space Command Remote Styles

[Oldstuff78]

I was searching eBay and saw someone had listed an old space command remote clicker. It got me to wondering when the round style buttons on them changed. Not having the luxury of having a old Zenith, I have no idea. I know all the roundies had round button remotes, but when did the other button designs come into place like the one listed here ?

http://cgi.ebay.com/ws/eBayISAPI.dll...E:B:SS:US:1123