Wow... good things come to those that ask. Thank you to an anonymous sender for their PM!   XLBOSS1.bin seems to be most likely the OS I remember, I a hex editor I can see the MEMOPAD replacement header "THE XL BOSS V1.0" and "LOAD ERROR" instead of "BOOT ERROR" , and 4KB of blank space at the beginning of the ROM   XLBOSS2.bin has a lot more data in the first 4KB, the original "BOOT ERROR" again, and I see the string "macromon xl © allen macroware" in hex editor, so the disk based macromon
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