Table: coins_info
Columns: value
diameter
thickness
mass
composition
edge
obverse
reverse
first_minting
issue
withdrawal
lapse

Question: What material is made with a rounded, plain edge?
SQL: SELECT "composition" FROM coins_info WHERE "edge" = 'Rounded, plain'

Question: How many coins have a diameter of 23mm?
SQL: SELECT COUNT("reverse") FROM coins_info WHERE "diameter" = '23mm'

Question: When was the coin with the mass of 3.7 g first minted?
SQL: SELECT "first_minting" FROM coins_info WHERE "mass" = '3.7 g'