Actually, after having a more thorough look into the documentation;
REMARK 3 might be the more relevant to what you need. Other tools are reported in that section.
REMARK 3 presents information on refinement program(s) used and related statistics. For non-diffraction studies, REMARK 3 is used to describe any refinement done, but its format is mostly free text.
From the same source as you reference yourself v 3.3, I would argue that
REMARK 0 would be more accurate than
REMARK 0 (updated), Re-refinement notice
REMARK 0 identifies entries in which a re-refinement has been performed using the data from an existing entry. This remark also describes the PDB code and the journal records for the original data set.
While when you consider the definition of
-- which follows directly:
REMARK 205 (specific to Fiber diffraction experiment),
REMARK 215/217 all specific to NMR experiment),
REMARK 230 (neutron diffraction study),
REMARK 240(electron crystallography study) and
REMARK 247: specific to EM study)
REMARK 250, Other Type of Experiment Details
REMARKs specific to other kinds of studies, not listed above.
REMARK 250 is mandatory if other than X-ray, NMR, neutron, or electron study. The format of the date in this remark is DD-MMM-YY. DD is the day of the month (a number 01 through 31), MMM is the English 3-letter abbreviation for the month, and YY is the year.
REMARK 265 is also about the crystallography experiment.
Hence, I know that personally, I usually assume that whatever is annotated in
REMARK 250is relevant to the first acquisition experiment to me.
Another reason I am more inclined to think
REMARK 0is more accurate, it is due that the definition of
REMARK 0 was updated while
REMARK 6-99 are are no longer for use of free text annotation.
BTW, I am not sure how Pdb_extract would do with the remarks when converting the PDB file to CIF files. It would probably worth perusing PDB to PDBx/mmCIF Data Item Correspondences page.