If I may suggest another collection type about which I have read an article by Mitch Sanders which appeared in ANA magazine 'Numismatist'. It's called 'Concentrated Collection'. I tried to attach the PDF of the article but it exceeds the size limit.
So here are the excerpts:
EVERY COIN collection
is unique, reflecting
its owner’s individual
approach to the
hobby. But while
there is considerable
diversity in what numismatists
collect, decisions about how to
collect generally focus on two well established
methods. A type collection
includes representative examples from
many different coin series, while
a date/mintmark collection aspires
to completeness within a single series.
Though different in focus—the breadth
of type collecting contrasts with the
depth of date/mintmark collecting—
they both have an important place
in numismatics.
A type collection provides a broad
overview of numismatics—20thcentury
U.S. coins, small cents, dimes,
Seated Liberty coins, or pieces produced
at the Carson City Mint—and typically
contains a single example of each design
type within the scope of the set. For instance,
a basic type set of 20th-century
half dollars would have a Barber,
Franklin, Walking Liberty and two
Kennedys (one with a standard reverse,
and one with a Bicentennial reverse).
Within a particular series, type sets
usually account for significant changes.
For example, at various times Kennedy
halves were 90-percent silver, 40-percent
silver or copper-nickel, and each
alloy is eligible for inclusion in a type
set. Also, major design subtypes, such
as the Lincoln cent’s Wheat and Lincoln
Memorial reverses, usually are
represented with separate coins. Minor
modifications in design or composition
also might be included, depending on
the collector’s preferences.
Assembling a type set generally is
very economical, both in terms of effort
and expenditure, because the coins chosen
from each series are entirely up to
you. If you’re seeking a Lincoln cent for
a type set of cents, small cents, 20thcentury
issues or coins portraying
Presidents, the common 1944 will serve
just as well as the rare 1909-S VDB.
Date/mintmark collecting, on the
other hand, enables you to pursue a
particular interest in detail by acquiring
every combination within a specific
coin series. This approach is more expansive—
as well as more expensive—
than type collecting. Not only are there
many more coins to collect, but sooner
or later, a date/mintmark collector will
encounter “key” dates, like the scarce
1916-D Mercury dime. Every date/
mintmark set also involves choices
about whether to include collector-only
issues like recent S-mint proofs, or
die varieties such as the 1955 doubled die
cent.
Your particular collecting approach
likely will depend on the interaction of
interest and budget. Series with many
inexpensive issues, such as Jefferson
nickels or Roosevelt dimes, generally are
good candidates for date/mintmark collecting.
For series that are more elusive,
or not currently major interests, you
might be satisfied with a single example
of the type.
However, there is a middle-of-the road
approach between the breadth of a
type set and the depth of a date/
mintmark set that I call “concentrated
collecting.” This kind of collection contains
one example from each decade of a
series’ lifespan, and one example from
every mint that struck them. Concentrated
collections are compact, because
the same coin can represent both a
decade and a mint.
Take the Morgan dollar, for example.
A date/mintmark collection has more
than 100 pieces, which can be quite
daunting to complete. On the other
hand, acquiring only a single example
might not seem sufficient for such
a sprawling series. A concentrated collection
falls between these extremes,
capturing the essence of the series with
only five coins. There are many ways
to represent the series’ five decades
and five mints, such as an 1878-CC,
1881-S, 1896(-P), 1903-O and 1921-D.
Whichever specific coins you
choose, a concentrated collection can
be a nice blend of breadth and depth.
Your collection is just that—your
collection—so its contents and development
should reflect your priorities
and your preferences. Whether you’re
pursuing a type collection or a
date/mintmark collection, or mixing
these methodologies, a definite collecting
approach will help you achieve
your collecting goals.