Your formula gives the number of occurrences, not the ordinal value
(i.e. where it appears within the series). The formula i
=COUNTIF($A1:$A$999,A1)
is helpful in determining the maximum value of the series (i.e. number
of times the duplicate appears).

Then I have (and I still am) completely misunderstood what you are after. In
an earlier reply, you said the following...

"What I'm looking for more than a flag, but rather an
assignment of a unique value of where that duplicate
occurs within the series of duplicates. So for example,
if Model1234 appears 8 times, the first time would
assign the value "1", the second "2", etc."

which you then subsequently requested to be ordered in reverse. Isn't that
simply numbering each occurrence with its count number, in order of the
count? Unless I am completely off base here, that is what the formula above
does... within each sequence of repeated model numbers, the repeated model
numbers are numbered from 1 to the number of repeats for that model. This
numbering of repeats is unique for each distinct set of repeated models. So,
if Model1234 appears 8 times, each row with Model1234 has a number from 1 to
8 next to it. In that same list, if Model9876 is repeated 4 times, each row
with Model9876 has a number for 1 to 4 next to it. If this is not what you
were asking for, then I am not sure how to read what you are asking for. Can
you show us a list of several model numbers, each with different number of
repeats, along with the numbers you want to appear next to them? That might
help clear up what you are asking for (at least, for me it will). Thank you.

Rick