WRT to us either displaying, static display, or Reds support we used ASCOT with a 4 figure suffix. If the suffix was 4xxxx then it denoted a Herc CMk1, it the suffix was 5xxx then it denoted a Herc CMk3.
In Personnel & Trg Command we used Station callsigns for displays (which might be personal), eg FYY xx for a Finningley a/c, CWL xx for a Cranwell based a/c.