Lil Baby's Jeweler Has a Plan to Avoid Another Fake Patek Philippe Blunder

Lil Baby's celeb jeweler is doing more than just profusely apologizing to the rapper for selling him a fake Patek Philippe watch ... he's taking costly action so it never happens again.

Gabriel Jacobs from Rafaello & Co. tells TMZ ... moving forward he's going to hire a professional watch authenticator who will inspect all the watches he sells ... to avoid another fake watch disaster.

What's more ... Gabe tells us anyone who has purchased jewelry from him can return and have it authenticated to assure them the jewelry's legit. He says he has no issue whatsoever with that in wake of the fallout from selling Lil Baby a fake Patek Philippe watch for $400k.

As we reported ... Lil Baby posed with the watch before hitting up the Met Gala but got pissed off after watch enthusiasts alerted him that the 40th-anniversary Patek Philippe Nautilus watch was a fake.

Rafaello & Co. issued a lengthy apology, copped to the mistake, refunded the dough and gifted the rapper 4 diamond rings. Gabe, who says he quickly righted the wrong because he wants to continue working with the rapper, doubled down a week later saying his mistake was not doing enough due diligence.

In fact ... Gabe says he showed the watch in question to 2 other dealers who also couldn't tell the Patek Philippe was a fake. That said ... Gabe insists it was an honest mistake.

He says he has NOTHING to gain by selling a budding rapper a fake watch. He also told us he gave Baby $3.5 million worth of jewelry to wear at the Met Gala ... so what's to be gained by selling him a fake watch?