「年号」has sort of stayed with me ever since a probing thread we had here thirteen years ago. This morning I encountered “designation” and out of the blue “reign designation” pops to mind. ’Tis a goody, should post it, thought I. Mac Dictionary defines this subsense of “designation” as:
“a name, description, or title, typically one that is officially bestowed”.
Of “reign designation” Google offers less than a couple dozen examples. Surprisingly few, it seems to me, for such a fine rendering, though most of them do involve a Chinese or Japanese historiographic context. In any case, it seems fair to say that this solid candidate for「年号」has undeservedly fallen between the cracks.
Wishing everyone healthy and even inspiring appreciation from your clients ~*