First step is to identify it by Scott number, and to do that you will want a perforation gauge and watermarking fluid. https://stampsmarter.org/features/S...rank_ID.html
Will then help you determine which variety it is.
Then you might look at eBay
past sales for that particular Scott number at which point you may be discouraged on the financial front if it's only worth a buck or two.
But you will have enjoyed puzzling out the identification — that's the most rewarding part of the hobby for many of us.