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In older Stanley Gibbons catalogues , "rox" and "7z" are occasionally found in text-dense lists describing stamps. : Likely a shorthand for Rose (a color).

: Often denotes a specific catalog sub-number or printing variety.

... paper as permitted by Regulation S-T Rule 101(b)(1):  ... ROX.\7Z?9B"RM$ED?1OV3_AOXGT/Q?XK\::VKP&&RD_:&^*GA_P $>!O" ML%W-:

The string "ROX.\7Z" (and similar variants) appears in the raw ASCII text of SEC EDGAR filings .

: These catalogs usually describe paper as "medium," "thick," or "wove" rather than using "Rox.7z" as a paper name itself. Technical Data and SEC Filings