A black surgical mask that Michael Jackson allegedly wore the night before he died in 2009 has hit the auction block — and the bids have already surpassed $20,000.

According to the auction house — Nate D. Sanders Auctions — MJ wore the mask (above) while rehearsing for his “This Is It” concert tour on June 24th, 2009 … the singer’s last ever rehearsal.

The auction house claims the mask  — made of silk fabric, personally designed by the King of Pop — contains visible traces of MJ’s stage make-up along with a strand of his black hair.

One of MJ’s former bodyguards was in possession of the mask, and swears by its authenticity. MJ famously wore surgical masks outdoors as a form of disguise.

The auction ends April 30th — and bidding has already reached $21,190. The auction house estimates the mask will sell for $50,000-$150,000.