The byte at position 0x40-43 represent four potential values for data block sizes and 0x44-47 represent 3 potential tag sizes in bytes (there is a possiblity there are additional values for these sequences which may require future adjustment to the signature) 0x50 defines the disk encoding. Byte 0x51 defines the 'format byte'. Bytes 0x52-53 are the private word/magic number used for identification. Further information is found here: http://68kmla.org/wiki/index.php/DiskCopy_4.2_format_specification
Details: File format summary
: detailed report on file format 
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