These are the first maps where photographic albedo was converted into exact numerical values.

Source: A photoelectric-photographic study of the normal albedo of the Moon, accompanied by an Albedo map of the Moon 1970

https://pubs.er.usgs.gov/publication/pp599E

Figure 7.—Isodensitracings made from the photographic plate used in the present lunar photometry. A. Contours corresponding to areas of geologic significance. B. Contours showing no geologic significance.