How old is my typewriter and how much is it worth?

I've had this old typewriter lying around for awhile now, and I never use it. I've decided to sell it, but have no idea how old it is or how much to ask for it. It is 1'x1', off-white and green plastic, with all the keys. It's manual, with a two-color ribbon on a spool. It's made by Royal, and has a logo that is a little box divided in half up and down, with the right side divided in half again to make a square with a circle on top. It has Magic margin ons, and on the top it says Sabre. I have the original case too. I don't know if this helps, but it looks kinda sixties-early seventies to me. Any info would be great!