This is one of those cases where it is suggested to get the
book before you buy the coins. ( and read the book)
When I was doing my
Jefferson nickel sets, I tried to read
as much as I could. Below is one of the books I was advised
get.

On pages 175 and 176, Q. David Bowers quotes Bernard
Nagengast's book, The
Jefferson nickel Analyst. A very
good book if you are going to do full step Nickels.
The book states
"Dark Philadelphia coins seems to have sporadically
appeared after 1945, as I have seen examples from 1946,
1948 and 1949. However dark coins from 1946 through
1950 are uncommon. The situation began to change in
1951, when many more dark nickels appear to have been
released. After 1951, the situation got generally worse.
Much of the 1952, 1953 and 1954 issues are dark. In 1955
things sunk to a new low, and virtually all of the 1955
Philadelphia coins have a darkish cast. For some reason,
1956 saw a sudden improvement, since most 1956 nickels are
brilliant. ... Philadelphia Mint returned to whatever it
had been doing before, resulting in steady deterioration of
quality in 1957 and 1958.
In 1959, bright coins became more prevalent. After the mint
apparently solved its dark coin problem, for I have never seen any dark nickels after 1959."
In the next paragraph
"the Philadelphia Mint did such a uniformly good job in producing black nickels in 1958,
that some enterprising coin dealers promoted the coins as "Black Beauties."
These coins have a certain eye-appeal, being uniformly
glossy or satiny black. There are some 1959 black beauties
as well, but they are much less common."
This information comes from two well known experts.
Of course I would be open to hearing other information,
if it comes from another well know expert.