Code designations have changed over the years. Fortunately, some older versions of MBAG's book "List of Codes for Special Versions (SA)" list the older and the newer descriptions.
E.g., the 3/93 version lists
598 as "heat absorbing glas, wrap around, band filter", meaning tinted glass, all windows and the top of the windshield is tinted darker, which was e.g. used for US cars (note: no heated rear window).
It also lists the later code 598 description, which was "heat-absorbing glass for side window panes and heated rear window pane (ESG), crystal clear windshield" (ESG= single-pane safety glass)
This latter use of 598 seems not to be valid for the W113.
Klaus
1969 280 SL