Also does anyone know if the lever next to the line spacing width lever is the carriage lock lever?  If so am i right in thinking towards the user is "LOCKED - for travelling" away from the user is "UNLOCKED - for typing."

The bad news is that you're missing at least one spring (see photos below), but the good news is that it's a spring that should be easy enough to source.

However, I would question the logic of wanting to fix the machine. The Corsair (along with others of the period) are terrible typewriters. And aside from the missing part, there seems to be other damage to the end of the carriage. You're missing the lever plastic for the platen release (it's not a carriage lock) and the plastic carriage trim in that area is cracked and missing pieces. There's also something amiss with the angle of line advance lever - it appears to have been bent outward, maybe it got caught on something?

My advice would be to buy another typer - an older Smith-Corona model would be a substantial upgrade in performance and quality to the Corsair. Actually, almost any other portable would be a better investment.

Good luck!

Jayson, the spring is approximately 21 mm in overall length. It's compressed/coiled section is around 14 mm. As for it's guage, it will of course have to fit through the hole at the end of the lever. Since it's a very common spring type I wouldn't think that you will have too much trouble finding one that will fit.

The platen release is not for the removal of the platen. The lever disengages the gearing for the line advance mechanism and allows you to freely spin the platen. Try it out and you'll see what I mean.

Good luck with the repair and let us know how you make out with it.

Beautiful photos and great detail, which makes all the difference when trying to troubleshoot a problem online. Looks to me like the tab on the backside of the line advance lever is broken off. It's that tab that hits the line selector and dictates how far the line advance lever will travel. 

Look at your third photo. The lever in question is the one attached to the spring and is currently hanging downward (it should be turned 180 degrees when it's properly positioned). You can see at the end of it a small tab that is bent toward the inside of the carriage, which is what engages the gear on the end of the platen to turn it. Just above that tab there should be another facing the opposite direction, toward the outside of the machine, which is what hits the line selector. Since it appears to be broken off the platen is probably always turning at least two lines at a time. 

Hope that makes sense. I hope that's all that's wrong, but without tearing my machine apart to compare, I don't see anything else that's obvious,

Jayson, you nailed the piece in question in your highlighted photo. The missing tab, which would be exactly dead center of the circle, goes through the opening the arrow points to.

I appreciate your efforts to repair this machine. Every typewriter saved from the scrap heap is a step toward preservation of these mechanical machines. And even if you don't get the part, the machine is still usuable, even if it does function more like a '30s Remington Cadet (they didn't come with a line advance lever!) than a '70s model.

I know you didn't spend a lot for the little plastic typer, but if you keep your eyes open, you should be able to find other machines for the same price that type 100 times better. Trust me, if your girlfriend was to try one of these better machines in comparison, she would see the light and realise that she was wasting her time with the Corsair. She might like typing with her Corsair, but she will LOVE typing with a better quality machine. Honestly, the difference is that dramatic.