Original Rodinal is p-Aminophenol in sulphite with no free Hydroxide, so similar but with a much higher level of sulphite.

The sulphite in Rodinal is generated by adding Potassium Hydroxide to Potassium Metabisulphite the difference beteween Calbe/Orwo R-09 and agfa (post 1963) Rodinal is the first has no free hydroxide, the second uses less developng agent at a higher pH wit an excess of Hydroxide.

Mees did similar in his early days at Wratten & Wainwright when he worked on p-aminophenol around 1908

Ian