According to pbr the first pic is a ribbed leg. Clearly it has a rib along the outside corner and one down each side almost the full length of the leg
leg-28rc (resized).jpg

The second pic is listed as a non-ribbed leg and matched the legs on the few gottlieb ems I currently own from 1976-1978. It still has the rib or ridge down the outside corner.
leg-28ca (resized).jpg

I order 27" non-ribbed legs and received the legs in the bottom of the third pic. Clearly no ribs or ridges at all, the corners are a perfect 90 degree corner and sides are perfectly flat and do not match any legs on the machines I have. The legs taped up in the top of this photo are the ones removed from my Jacks Open and have the single ridge down the outside corner.
non-ribbed leg (resized).JPG

Either I have received the wrong legs or the pic of a non-ribbed leg is wrong ? All the pics I can find of gottlieb ems from these years have the legs with a single rib down the outside corner ? Does non-ribbed actually mean a single rib down the outside corner and if so what are the legs with two perfectly flat sides referred to as ? Isn't there actually three types: multi-ribbed; single-ribbed and non-ribbed ?