tandum shwinn bike

i picked this bike in some ones throw aways on the side of the road. it was and still is fully functional. all i had to do is replace the inner tubes, which i did. i plan on restore it. i dont know what year it is or what the value is. i would love to find out how old this bike is and what the retail value would be. i realy like this bike alot cause it has the old school look and its the same color as my other restoration project which is a grabber blue 1970 mustang(which is my pride and joy/prized possession). i hope to have both fully restored so i can take both to shows a cool pair at the show. it dose have some rust on the chrome fenders and handle bars, which i plan on fixing of course. but thats my awesome pick . if anyone has any info on this that would be awesome