Check out these interchangeable ornamental caps. The three ornamental cap blocks, in the center, have a square slot cut into them. This slot allows different letters of the alphabet to be exchanged when printing. The two letters (“A” & “N”), on the left and right, are printed examples of this. I scanned them from my original 1715 Apocrypha.  Printers in the 18th century often used these interchangeable ornamental caps, but not always. Below those, you can also see  a couple of letter “A”s that has been carved within their own decorative scenery and are not interchangeable.  I scanned both of these from this same Bible as well.