The first twelve volumes of this annual (apart from #1) also came with a dust-jacket which would add up to 20-25% to the value. 1964 was the first annual without a dust-jacket.
The early ones are lovely looking annuals but it's sad that as time goes by the collector market seems to be diminishing and so values are static if not falling.
Note: some PR issues may have no value. Selected issues in FN, VF or VF/NM may not exist in some titles.