Welcome to the community. These were in use from about 1918 through the 1950s (for this style) and sell on eBay for US$3 - $8. You can still buy IRCs today. http://www.ebay.com/itm/SOUTH-AFRIC...AOSw4shX-TzB Note: The one you show in the image has some condition issues. There are a few that command more depending on cancellation; perhaps someone who specializes in these will reply. Don
According to "An Illustrated Guide to Imperial Reply Coupons and Commonwealth Reply Coupons" by Peter Robin (2009), this is South Africa #1 and has a scarcity rating of VR (Very Rare) and is valued in 2009 from $26 and up. But condition plays a very important part in value.
This is a generic Lausanne type coupon issued from 1974 to 2001. You can't tell what country it came from since there is no country name. Some countries had their names imprinted on the coupon, but didn't have any value. Others had a value imprinted but no country name. Finally, there are some that had both the country name and a value printed. I don't think Canada had name or value printed on any coupons of this type.
For US readers: in 1998 (?) there was one printing that had UNITED STATES OF AMERICA imprinted along with the value of $1.05. These are extremely rare. Other US coupons of this type had no country name but always had a value printed in red.