[ICDP]

Originally Posted by lane

Hmmm, it comes to mind that the publication date of 20 March 1940 for A.P. 1590B/J.2-W, Merlin II and III – Use of + 12 lb./sq.in. Boost Pressure followed actual unit conversion to 100 octane/+12 in the field in some cases; see for example 602 Squadron Operations Record Book, 151 Squadron Operations Record Book, 111 Squadron Operations Record Book & 74 Squadron Operations Record Book - Fwiw.

Remember your linking to info on the Merlin II and III, the document Seadog is linking to is for a Merlin XX. The Merlin XX was not used by fighters during the Battle of Britain so its boost rating is irrelevant since we don't have any flyable plane in CoD with a Merlin XX.