A few additional observations here on the subject. Some guns having keys with heads entering on the left side, have no silver shield, while on the right opposing side there are inlaid silver shields, (an early S. Baum, notably); another, (same maker) put the keys in from the left side and had a silver shield on the left side as well as on the right side. Why? Who knows? Many seen to have simple flat keys with no head. Most I have seen fall into the latter category since key heads required much more work. In any event, those with heads mostly seem to enter from the left side.
Some makers who used pins, tapered them and you have to remove them from the bigger ended side. If you don't you risk hollowing out the hole as you punch the pin through from the wrong side.
You need to look at a number of originals to see the numerous variations. When in doubt, use barrel bands, and don't forget the sling swivels.
Hope any of this makes sense. It is at least as understandable as JTR's convoluted descriptions, without the statistical analysis.
Reekie