1942 and Ultima Reserva both represent the pinnacle of tequila-making, but have slightly different approaches. 1942 is aged just short of the threshold for extra-añejo, and uses the spirit from just one specially selected pot still.
Ultima Reserva meets the extra-añejo threshold, and is aged using a sherry-style solera system - each bottle contains a small amount of spirit from Don Julio's final agave harvest.