Quote:
do I keep them as stamps, or sell them as Cinderellas?
Well, first of all, there is no definitive definition of a Cinderella.
Some people would use a broad definition, pulling in locals, revenues and things like international reply coupons. Others would restrict the terms to things like charity seals, promotional labels, bogus issues, etc.
But even if they are "cinderellas" by which ever definition that you want to use, why base your decision on whether to save or sell on that? If you find them interesting, save them. If not, sell.