SHEETPROTECT (0x0867) is defined to have a default length of 23 bytes. However this record type can also have a length of 19 bytes.
In this alternative configuration the last 4 bytes which normally hold the option data are missing. Also the signature bytes are 0,3,0,1,0,0,0,0 not 0,2,0,1,ff,ff,ff,ff
Bill Seddon