The early ones were Keilwerth New Kings, made by Keilwerth in Germany, stenciled for Couf (Armstrong). They are identical to the King Tempo (although with the King there's apparently some overlap with an Amati-made horn.....I think.)
Later models (the Royalist II) may have used some Keilwerth parts (body etc.) but my understanding is those were more student-line, actually built by Armstrong in the US, and are not as good as the early ones.
Keilwerth used their New Kings as a stencil for many distributors in Europe. They are intermediate or better (depends on you, the player). The early Superba II Couf models were also New Kings.
A Keilwerth-made Couf will have the Keilwerth-style conical keyposts. Armstrong-made Coufs won't.