This below is from p. 41-2 of Kropp’s book. I’m suspicious of this interpretation of 422/1. I’ve ordered the citation from ILL but as far as I know the comparative visual evidence is all much later…
The saddle stuff is fascinating though! Esp. That the Roman designer of the type knew enough to include it. The other similar type from a few years later doesn’t show the same saddle (431/1).
Liv Mariah Yarrow 