Diddy's Puff Daddy 'Bad Boy 4 Life' Signed Guitar Hits Auction Block

Diddy's guitar autographed with his former Puff Daddy moniker is going up on the auction block -- and experts are watching to see if his public downfall helps or hurts the final price.

GottaHaveRockAndRoll is expecting upwards of $2K to be splashed out on the electric guitar that boasts the inscription "Luv, Puff Daddy, Bad Boy 4 Life" in silver felt-tip pen -- a nod to his 2001 hit song with that title, and the mogul's label Bad Boy Records ... home to rap legends like Notorious B.I.G.

The instrument comes with a James Spence Authentication (JSA) Letter of Authenticity, and a Gotta Have Rock and Roll Certificate of Authenticity ... so, bidders know they're getting the real thing.

The listing is part of the site's Hip-Hop auction, which begins Wednesday ... and also includes other items like Biggie Smalls' autograph and Kanye West's signed boots.

As for the Diddy guitar ... it's no surprise the bidding probably won't reach astronomical heights, given the controversy swirling around him.

As you know ...  the feds are on his tail, and he's facing a barrage of lawsuits with some pretty serious allegations. On top of that, the brutal video of him beating his then-GF Cassie surfaced last month.

Of course, controversy sometimes fuels higher bidding at some auctions. Don't forget, plenty of O.J. Simpson-related items have been auctioned off for years.