I have a collection of pennies from my great-grandma that spans from the 20s to the 60s. Each roll of pennies is organized by the decade (ex. '1940s' ). Which decades are the most likely to be profitable and worth opening up the rolls to look for high-value picks?
Welcome to Coin Talk. IMO all the key Lincoln cents were struck in the Teens, 20's and the 31=S in the 30's. There are semi-keys from the other decades and varieties &/or errors like the 1955 & 1972 DDO's, 1943 copper cent, etc. The value of any coin depends a lot on the grade so you can have common date cents from any decade be worth money if the grade is high enough (MS-68 or better).
Hopefully your G Ma put away some good coins. Don't forget the RPM's Here is a variety site that is well recognized around here. http://varietyvista.com/index.htm Take a look if you have any questions just ask. This is Coin facts by PCGS It can help you see what each grade looks like and an auction price that each coin sold for. This is only for graded coins not raw. https://www.pcgs.com/coinfacts