A reprinted Flashlight? What gives FFG? Well.... Not quite!
First off, an Old Keyring only spends charges on successful tests. A Flashlight is best used to automatically beat low difficulty locations, a great way for low- characters to get clues in any difficulty, especially with low player counts. However the risk of failure when you turn a Flashlight at a high-shroud location is great and often not worth it, an all-too familiar issue for a 3- character trying to tackle a 4-shroud location.
Old Keyring shares the Flashlight's ability to beat a low shroud location, but the fact that charges are only spent on successes means that you can MUCH more fearlessly blast a 3-5 shroud location with repeated investigate checks until you eventually hit all the clues, Old Keyring basicly reads "+2 until you've discovered 2 clues", a rather terrific ability.
Finally, this card self-discards right after success. Self discarding means that cards like Resourceful can recover the Old Keyring, more importantly, Old Keyring + Scavenging are a natural combo! It's actually ridiculous if you consider the upgraded Scavenging, investigate a location, finish the Key, immediately replay it! This is now one of the go-to combos for clue strategies.