I view this set as a conservative investment, based upon the the growth of interest in stamps of the British Commonwealth. Also, it's inexpensive and scarce enough that it's value would receive an additional boost should a significant stamp market develop in Gambia.
A nation of 1.7 million people, Gambia has a liberal, market-based economy characterized by traditional subsistence agriculture, a re-export trade built up around its ocean port, low import duties, minimal administrative procedures, a fluctuating exchange rate with no exchange controls, and a significant tourism industry. Annual GDP growth has averaged about 6% over the last 5 years.
Information concerning printing quantities of stamps is often useful in determining which may turn out to be good investments. The StampSelector Scarce Stamp Quantities Issued List (SSSSQIL) currently includes over 9,700 listings of stamps and souvenir sheets with issuance quantities of 100,000 or less.