The lever on the back to change presser feet is a fairly new invention. Singer started it in the 70s or maybe 60s.
The Singer version is a narrow steel snap on adapter with no lever. The one with the lever is more or less a universal adapter that all the makers use today.
The adapter is attached to the presser foot shaft with a screw, just like normal feet. However those with the lever type are usually attached with a slotted screw instead of a thumb screw.
You can get the lever type adapter and feet for it, along with the thumb screws from Sew-Classic {
http://www.shop.sew-classic.com/ }. They also have an assortment of regular presser feet for you get.
Joe