MATCHPOINTS
you are in 2nd chair (RHO passed). You play a standard system with 1NT 15-17HCP. Purpose is to determine whether hands of this type (with 2 four-card majors and a small doubleton outside here) would make you consider opening 1♦. Also, perhaps some would consider this hand "too good" for a 15-17 1NT and are opening 1♦ because they feel it is worth an upgrade in addition to having both 4 card majors.
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