The Corrigendum SI stated that:
MBH98 made use of all nearly continuous monthly gridpoint surface temperature records (no single gap greater than 24 months, and no more than 10 years of total missing data.
I checked these criteria against the temperature dataset archived at the Corrigendum SI and found that 242 out of 1082 gridcells selected for the 1902-1993 period failed one or both criteria, while 229 gridcells in the 1854-1993 ( rather than the 219 shown in MBH98) met both criteria. Some curious differences between newer and older HadCRU versions are noticed in passing. More