in addition to wolfsoul his topics, some more tests that show at least a few things:

Junior 7.87
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15 * iron net boots + wolf tooth + iron net boots

skeleton iron sword: 11
ice bracers: 3
iron boots: 1

Primary 15.14
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11 * skeleton iron sword + black jade

ice bracers: 3
footman's helmet: 3
iron claw: 2
bowling: 2
vine shoes: 1

Junior 7.87
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10 * copper crest + wolf tooth + copper crest

bronze helmet: 1
skeleton sword: 3
pirate's hat: 2
ox horn hat: 2
crescent claw: 1
copper armor: 1

i won't compound these anymore, the results are simply not profitable enough. But still it shows a few ideas if you need skeleton iron sword or so