LAMOST spectrum of the PG1159 star RL 104 (blue graph). Overplotted is the final model (red) with T_eff = 80 000 K, logg = 6.0, and element abundances as given in Table 4. We note the unusual presence of highly excited C IV lines at locations indicated by horizontal blue and green bars (with principal quantum numbers marked). They are not included in the model. Line identifications in brackets denote lines that are not observed but potentially constrain the atmospheric parameters as discussed in the text. Diffuse interstellar bands (DIBs) are indicated.