Negretti Zambra Ambrotypes Crystal Palace 1850's

I recently purchased these at a local auction, they have labels that read Negretti Zambra, Ceramic Court, Crystal Palace, Sydenham. Research shows that NG had a studio selling optical equipment and photographs in the 1850's. I've had a few emails suggesting that they are Ambrotypes and not Daguerrotypes any hints or information to determine exactly what they are would be appreciated.