Difference between part types?

I've tried googling and I've been able to learn about all the parts except these.

Can someone post pics and how to identify a

•SA Type II and Type III lockbar sight?
• SA long fork VS short fork follower rod
• SA WWII gas cylinder vs post war gas cylinder

Thanks a bunch guys!

If you buy Scott Duff's book The M1 Garand: WW2 it has the illustrations you seek. Also Poyer and Riesch has illustrations, but they have a degree of misleading info in spots...then you don't have to wait, you can research to your heart's content.

Try looking at ebay