Followers of Durer with a keen eye will recognise this model from several study pieces completed by the artist, most likely it was a local man who could be relied on at short notice. Both artworks feature his standard use of white heightening for the elements intended to hold more light, or at least to give that impression. Other sections would then be darkened to produce the opposing shadows.
The elderly man's key features are his balding lightened forehead, and long unstyled beard. Light is also added to his furrowed brow and protruding roman nose which helps to draw the sketch out from its flattened nature. The artist focuses on his wrinkles but the elderly man skin actually appears fairly smooth in this flattering portrait.
Albrecht Durer chooses not to add a neck or any clothing in this piece, suggesting that he was placing this element within another painting and wanted to perfect the gentlemen's facial features before adding a near copy of it into a larger piece. It would always be easier to make changes at this stage than later on when other features had been added.