Seems OP to always have Favor of the Sun builded into your investigator and have access to Ancient Covenant and also start with 5xp by keeping the old back. No reason to ever go classic Mateo unless you specifically want to run Blessing of Isis or some full support style. But even then its debatable what's better

Here's an idea for when you break out those early scenarios where this card is the most problematic.

Errata it to have Victory 1 if it places a doom on the agenda. No victory if you cancel it.

Fixes a few problems. First you can never get hit by each copy more than once and you get a bit of a bonus for the acceleration comparable with playing a Delve Too Deep which can be nice boost on some of those super low exp early scenarios.

This card seems particularly interesting in Darrel Simmons. Not only is it a good enemy management tool allowing him to evade with his base 5, he also discovers a clue in the process, immediately moving the evidence from the enemy to his Kodak. This solves the puzzle of getting the evidence from an enemy drawn during the mythos phase and engaged to Darrel, usually in that situation the goon would start his turn first and defeat that enemy before Darrel can get the evidence.

Outside of obvious overachieve rogue synergy, this card, being Practiced, can be very very strong for Amanda Sharpe with a bit of setup.
Sure, you need to pass a test with a base value of 3, but if you have a couple of static boosts, start your turn with an easy enough test or are willing to spend some of the other skills you will surely have in your hand (you're Amanda, after all), you will just snowball the entire turn into a series of almost-auto successes.
This card is not balanced around being able to chain it 2 tests in a row, let alone 3.
It's a shame the effect lasts until the end of the phase only, or it would be an execellent encounter protection as well.

Cleaning Kit Makes this much simpler to use, and opens this up as a semi-reliable primary weapon in any investigator that can take both. ( Venturer did too, but Cleaning Kit's primary advantage is you don't need to exhaust, so you can blow through the ammo much faster on the turns you need to.)

Which is most guardians, but also Joe Diamond, Jenny Barnes, Kymani Jones, "Skids" O'Toole, Diana Stanley, William Yorick and the two neutral investigators.

a +3/+3 per shot weapon is pretty good, even if you need to over-succeed. In Guardian investigators, you could even use Cleaning Kit (3) once per round for an additional +2.

Is this better than just grabbing a giant hammer? Maybe not, but this is more usable than it used to be.