Cassette storing case

A cassette storing system for housing one of a first cassette and a second cassette, comprising:

• a) a first cassette having a first length L1, a width W, and a first height H1,
• wherein the first height H1 is shorter than the first length L1 and is shorter than the width W,
• wherein the first cassette includes a top surface having the width W and the first length L1 and a bottom surface having the width W and the first length L1, wherein the top surface includes a main portion that is the first height H1 from the bottom surface and a stepped portion that is a distance less than the first height H1 from the bottom surface, and
• wherein the first cassette includes a first front surface having the width W and the height H1;
• b) a second cassette having a first length L2, a width W, and a second height H2,
• wherein the second height H2 is shorter than the second length L2 and is shorter than the width W,
• wherein second height H2 is greater than first height H1,
• wherein the second cassette includes a second front surface having the width W and the height H2, wherein the second front surface includes a first recess;
• and
• c) a cassette storing case, including:
• a case main body including a bottom plate and a rear wall fixed substantially perpendicular to the bottom plate, and a first protrusion cantilevered from an inside surface of the rear wall, and
• a lid connected to the case main body,
• wherein the first protrusion has a first end face substantially parallel to the rear wall that is a first distance d1 from the rear wall, a second end that is a second distance d2 from the rear wall, and a protrusion top surface that extends from the first abutting end face to the second end, wherein the second distance d2 is greater than the first distance d1;
• wherein when the first cassette is housed within the case main body, the first abutting end face of the first protrusion abuts the first front surface of the first cassette and the protrusion top surface abuts the top surface of the first cassette;
• and
• wherein when the second cassette is housed within the case main body, the first protrusion is inserted into the first recess of the second cassette.