(I did consider your suggestion of Fin too. The opening stroke - like an opening paren - and the possible r (though the horizontals have different curvature from other examples in the poem) could have been f, then the i with super horizontal with flourish could have been -in or -inis. But I couldn't find a letter f with that form. I also don't know why you'd need it when you have the Explicit there. (and I don't know when fin/finis was used))

Mick