The information for the DS420 is clearly wrong: there never was an engine with a 5-digit number. This bulletin dates from December 1970, and in this month the engine numbers were in the 7M17xx and 7M18xx range (numbers were never used consecutively). Highest engine number at the end of the production in 1992 was around 7M0062xx. The 00-prefix to expand from 4-digits to 6-digits was added somewhere in 1983.
Also, the compression prefix -8 was used until it was replaced by -S around August 1971.