RUSTIC CAPITALS
Since Rustic Capitals are originally and ancient Latin script, the letters J, K, and U wouldn't have original sources, right? So, for this exemplar, are those letters your interpretations of what they would look like or did you reference another exemplar? Also, my understanding is that, in cases such as these, the non-canonical letters would have been created using strokes seen in the other letters and it does look like that was the case here. It seemed like a fun exercise to see if I could figure out how the letters were created, so I spent some time looking at them.
After studying the script, I would say that the non-canonical letters were created in the following way:
1. J: The downstroke and top cross bar appear to be what you would get if you took the downstrokes of E, F, and T, plus the bottom cross bar and turned them upside down. The bottom curve looks the same as the bottom curve on S, B, and D, which makes sense if you compare S, B, D, and J look in a standard printed font.
2. K: The left half (the downstroke) is identical to I, while the right half looks like what you would get if you took the X and cut it in half down the center vertical axis.
3. U: This is a tricky one. It looks a lot like a miniscule italic v to me (but done large). The left side looks just like the V, but I'm having trouble with the inspiration for the right side. It might be the same as part of the right side of the O but I would need to print it out and lay them over each other on a light box to know for sure. Mostly, it looks like a softened version of V, which I suppose U is.
So,
@Ken Fraser am I correct in my interpretation (if you used a reference for those letters, then you wouldn't be able to say for sure of course, but you could say if you agreed with me or not)?