One way to hold obverse: a coin lying in your palm, head up. The side looking back at you is the obverse; turn it and you get the reverse. Two things follow from that picture. First, the word is about the side that faces the viewer, which is where the adjective comes from. Second, the two sides belong to one object, so when the word is used about situations it never means an opposite standing somewhere else. It means the other face of the very thing you are holding, which is why defeat can be called the obverse of victory.
From the word’s history
The packet's source gives only this much: from Latin obversus, entering English in the 1650s. It gives no gloss for the Latin, so nothing further is claimed here. What the source does record is the adjective sense 'turned or facing toward the observer', and that sense sits closest to the core image.
來源只給到這裡：來自拉丁文 obversus，大約 1650 年代進入英文。它沒有為那個拉丁字附上字義，所以這裡不多說。來源確實記下來的是形容詞「轉過來面對觀看者的」，而這個意思離核心畫面最近。
Wiktionary, "obverse"
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