@@shanez4545 No.77 is the string quartet number in the Hoboken catalogue, which is different from the opus number. The Hob. numbers number each quartet separately, while the op. numbers group quartets, e.g. op. 76 comprises 6 quartets. Furthermore the op. numbers also number works by Haydn other than his string quartets. Haydn's string quartets are indeed better know under their op. numbers than their Hob. numbers.
