I have the following table and I am having trouble deriving a formula for my
answer:

Store # Item #
#0111 ADSD200.21SP
#0111 ADSD200.22SP
#0111 ADSD200SP.21.12
#0111 ADSD200SP.21.12
#0111 V29K10007.7SP
#0111 V29K10007.7SP
#0119 OG313
#0119 OG313
#0202 CF101-S
#0202 CF101-S

I would like my answer to look like this:
Store # Item #
#0111 ADSD200.21SP Unique
#0111 ADSD200.22SP Unique
#0111 ADSD200SP.21.12 Unique
#0111 ADSD200SP.21.12 Duplicate
#0111 V29K10007.7SP Unique
#0111 V29K10007.7SP Duplicate
#0119 OG313 Unique
#0119 OG313 Duplicate
#0202 CF101-S Unique
#0202 CF101-S Duplicate

Is this possible? Please help.