After getting 4 Compound ATK-04s in 4 days, I finally got my first ring from a Promethium lockbox today from trash mobs from a failed FOS 2 run (where Lex bugged out). It's a healer ring too! Stats are as shown below. The only flaw is that its socket affinity is 14 precision. If modded with resto III (29 resto), it would give me 65 resto from a single ring. That's more than double the resto amount from the Central City healer ring (24 resto). It's account bound, meaning that you can trade the ring between characters. However, if you mod it, it will become integrated to your character. So I'm still in a quandary whether to mod it or trade it to an alt.