There are only 4 types approved in this category and they are 10 years old, 20 years old, 30 years old, and over 40 years old. These are a blend of many years where the average age of the bottle is at least 10, 20, 30 or 40 years old (in the US market ONLY this is called 40 year old, for legal reasons that I won't bore you with here).
They are typically produced in a “House style” that varies from producer to producer yet remains relatively the same from year to year. It is the Master Blender responsible for exhaustive work at blending these Tawnies that has maintained the reputation of the "brand" and the Port Shipper's "house style." The consistency of the particular house style is the primary goal of the winemaker and master blender, along with producing a wonderful wine year after year. These Tawny Ports often give excellent quality to price ratio, (QPR) allowing the buyer to get an older Port at an affordable price. Tawny Port with an Indication of Age is what most Tawny lovers seek out, except those that have been enlightened by Colheita which is gaining prominence in the US and is still very difficult to come by in the UK marketplace.
The ages mentioned are not the minimums allowed in the bottle, but they are actually the average age of the Tawnies that are blended into the bottle. In theory, a 30 year old Tawny may have five year old Tawny that is balanced by a fifty five year old blend...and may have many different vintages blended into the same "lot" as well. Port Shippers that have an eye for quality and a concern for the long term "image" of their brand's consistency, add a year or two to the average age of the wine blended in their bottles. Therefore instead of having a 20 year old just meet the requirement...the savvy Shipper might add some Tawny with extra age that might actually balance out to 22 years.
Look on the label of a Tawny Port With An Indication Of Age and you will find the year of the bottling, the age of the wine 10, 20 etc., and a mention that the wine is aged in cask (or wood). These wines offer a smooth and silky mouth feel, with intense flavors and aromas that vary from nutty, caramel, nutmeg, leathery, and even chocolate. I will list a few brands for each of the four types of these Tawnies that I feel are good representatives.
Some personal favorites:
10 year old Tawnies that I do enjoy are Ramos Pinto, Ferreira, Niepoort, Kopke, Sandeman and Graham’s.
20 Year Old, is what great Tawny is all about! The color has now matured to a tawny hue, the tannins softened, the layered nuances dance on the palate, and complexity is understood after the very first sip. More importantly the QPR is in synch with the juice and you won't mind paying for these memorable bottles. Look for these winners: Ferreira's Duque de Braganca my personal favorite, Taylor, Quinta do Portal, Sandeman and Niepoort.
30 Year Old, For my money they do not offer much more than the 20 year olds and are at times too cloying/syrupy, with excessive sweetness, and the difference in complexity is not worth the price...again just my opinion here. Dow, Fonseca, Offley and Vista Alegre offer the top examples of this style.
40 Year Old, show dark amber colors and with all this time in wood have developed incredible characters. Quinta do Noval makes an excellent version, Sandeman, Graham, and Taylor make up the balance of my favorite 40 year olds.