The Testarossa was one of the cars that got me into cars; as a child, I had a 1:18 size red Testarossa toy car - this is my earliest memory of a specific childhood toy.
The Ferrari Testarossa is one of the most iconic cars for both Italian sports cars and the 80s as a decade. Although it wasn't the only Ferrari in the show, many people remember the Testarossa from Miami Vice (although I am slightly too young to fall into this demographic).
Like most cars, the Testarossa underwent updates every few years; these small incremental changes can drastically change the value and desirability of a given example. The very first Testarossas only had one mirror (distinctively mounted on the driver's side roofline), but this changed to a standard two-mirror design a few years into production.
The 512TR was the first major update to the Testarossa, and is often the most sought after model of Testarossa due to the increased power output and usability upgrades, such as improved clutch and shifter engagements. The 512TR can readily be identified by spotting the facelift front foglights, updated wheels design, and black engine cover / third brake light (US spec). You can see some of these design differences between the standard Testarossa and the 512TR, including the changes to its flat-12 engine, with the two versions parked side-by-side below.
(I still have never seen an F512M (the Testarossa's final version) in person.)