guest johnnie the notes you describe are g e bflat b, g diminshed is g bflat and d flat.
there is a chord shape often used in blues, which is the b7 shape up one fret, this is c major seventh c e g b, is this the chord u mean, it is often used between c#7 an b7, so third fret b 7 shape second fret b7 shape, first fret b7.