In {HEAD ~ the casing} 10 of {TAIL ~ the illustrated embodiment} constructed as described above, both the slider 20 and front cover 22 are positioned to close the opening of the casing body 12 during non use of the magnetic tape cassette, to sealingly keep the magnetic tape element within the casing 
of
In { HEAD ~ the casing } 10 of { TAIL ~ the illustrated embodiment } constructed as described above , both the slider 20 and front cover 22 are positioned to close the opening of the casing body 12 during non use of the magnetic tape cassette , to sealingly keep the magnetic tape element within the casing
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