In addition to the mark numbers, Merlin engines were allocated experimental numbers by the Ministry of Supply (MoS) – e.g.: RM 8SM for the Merlin 61 and some variants – while under development; these numbers are noted where possible.
Ud over versionsnumrene fik Merlinmotorerne tildelt eksperimentalnumre af Ministry of Supply (MoS) – for eksempel: RM 8SM for Merlin 61 og nogle underversioner, mens den var under udvikling; disse numre er inkluderet hvor muligt.