
The two versions of the Precious Memento are quite a reliable soak components on their own, though I didn't pay them much attention until now. I'm currently going through my first run of Edge of the Earth, playing Daniela Reyes, and as I wanted as much soak as possible, I only realized now that these are not unique (there's no symbol on the card). Plus, the limit restriction only applies to the particular type of memento you're playing : From a future life or From a former life. This means you could potentially get the two versions of the memento in play at the same time, by just getting another accessory slot from whatever source you could afford (hence the very basic yet very powerful Relic hunter.
This is a 11xp investment, but early on in a campaign it can make a big difference if you manage to get that many xp at the end of scenario 1 or 2. Not everyone will want to get them both, often you'd prefer the campus boy or his mirror sister that come cheaper and tend to find more uses in general cases, but in a niche deck that want to take damage to do-whatever-you-wanna-do-that-for, it' a powerful investment, arguably an infinite damage/horror soak that lets you have some other allies or hand slots to close the case.
10/10 would recommend.