Here's mine. I forgot. The windage just screws off by hand and is smaller. The elevation turret turns, and marked for varying distances. But the cap gets unscrewed at the top, and yeah, you have to hold onto it, or place it in the lowest setting I believe. Actually, probably the highest setting. (500)
I don't know what brand mine is. It was bought with my Colt A2 20" which is kind of old, and I've since painted it, obviously. But it was not a "colt" brand. Some kind of knock off. It still works though.
I will say this, it moves around in my A2. It didn't move as much in that removable carry handle pictured below. And I once had it on an A1 and did a session with it benched. The scope was real tight and that thing shot really great. I should've never got rid of it. It was an SAK barrel and I was getting 2 MOA consistently with just about everything I put through it. 1/12. I'll see if I can find pics of that.
this was my Navy Seals poseur look. Sorry!