Paint code “Unknown at this time “

What year is the car? Some paint codes have a letter preceding the letter and number on the tag. It corresponds to the year of the paint code. My 1970 Swinger has B5 on the tag, but EB5 on some of the old paint codes, E for 1970 B5 blue. I've been told that B5 blue is slightly different for each year it was availible.